The Selective NMDA Receptor GluN2B Subunit Antagonist CP-101,606 with Antidepressant Properties Modulates Cytochrome P450 Expression in the Liver

Recent research indicates that selective NMDA receptor GluN2B subunit antagonists may become useful for the treatment of major depressive disorders. We aimed to examine in parallel the effect of the selective NMDA receptor GluN2B subunit antagonist CP-101,606 on the pituitary/serum hormone levels and on the regulation of cytochrome P450 in rat liver. CP-101,606 (20 mg/kg ip. for 5 days) decreased the activity of CYP1A, CYP2A, CYP2B, CYP2C11 and CYP3A, but not that of CYP2C6. The alterations in enzymatic activity were accompanied by changes in the CYP protein and mRNA levels. In parallel, a decrease in the pituitary growth hormone-releasing hormone, and in serum growth hormone and corticosterone (but not T3 and T4) concentration was observed. After a 3-week administration period of CP-101,606 less changes were found. A decrease in the CYP3A enzyme activity and protein level was still maintained, though no change in the mRNA level was found. A slight decrease in the serum concentration of corticosterone was also maintained, while GH level returned to the control value. The obtained results imply engagement of the glutamatergic system in the neuroendocrine regulation of cytochrome P450 and potential involvement of drugs acting on NMDA receptors in metabolic drug–drug interactions.


Introduction
Knowledge of the regulation of liver cytochrome P450 by drugs and toxic substances at the level of the hepatocyte is already broad, however, physiological regulation of its expression, especially the role of the nervous system has been the subject of research only for the last decade. Since secretion of hormones regulating cytochrome P450 genes (e.g., growth hormone, corticosterone and thyroid hormones) is under the control of the brain nervous system (mostly by the hypothalamus), therefore, the changes in brain neurotransmission can affect endocrine regulation of cytochrome P450 in the liver. The neuroendocrine regulation of cytochrome P450 has already been shown to occur via the brain dopaminergic [1-3], noradrenergic [4][5][6] and serotonergic [7][8][9][10][11][12][13] systems.
A potential involvement of the glutamatergic system in the regulation of cytochrome P450 expression has not been examined so far. Immune-histochemical studies have shown that the hypothalamic paraventricular and arcuate nuclei are deeply innervated by the glutamatergic system and are rich in all subtypes of glutamate receptors [14][15][16][17]. There is a dense innervation of growth hormone-releasing hormone (GHRH)-containing neurons in the arcuate nuclei, as well as of corticotropin-releasing hormone (CRH), thyrotropinreleasing hormone (TRH) and somatostatin synthesizing-neurons in the hypothalamic paraventricular nuclei. Furthermore, glutamatergic innervation of the hypothalamic median eminence arising from different hypothalamic structures has been described [18,19].

The Effect of CP-101,606 on the CYP2A Activity and Expression in Rat Liver After 5-day and 3-week Treatment
The activity of CYP2A, estimated as the rate of the 7-α-hydroxylation of testosterone, declined to 68.7% of the control after 5-day treatment with CP-101,606, but no changes in the CYP2A protein level or CYP2A1 and CYP2A2 mRNA levels were observed ( Figure 2). The CYP2A activity reduced by 5-day treatment returned to the control value after 3 weeks of treatment with CP-101,606.

The Effect of CP-101,606 on the CYP2A Activity and Expression in Rat Liver after 5-Day and 3-Week Treatment
The activity of CYP2A, estimated as the rate of the 7-α-hydroxylation of testosterone, declined to 68.7% of the control after 5-day treatment with CP-101,606, but no changes in the CYP2A protein level or CYP2A1 and CYP2A2 mRNA levels were observed ( Figure 2). The CYP2A activity reduced by 5-day treatment returned to the control value after 3 weeks of treatment with CP-101,606.

The Effect of CP-101,606 on the CYP2B Activity and Expression in Rat Liver After 5-day and 3-week Treatment
The activity of CYP2B, evaluated as the rate of the 16β-hydroxylation of testosterone, was diminished to 74.8% of the control after 5-day treatment with CP-101,606, though no change in the CYP2B protein or CYP2B1 and CYP2B2 mRNA levels were observed ( Figure  3). The CYP2B activity diminished by 5-day treatment returned to the control value after a 3 week-treatment with CP-101,606.

The Effect of CP-101,606 on the CYP2B Activity and Expression in Rat Liver after 5-Day and 3-Week Treatment
The activity of CYP2B, evaluated as the rate of the 16β-hydroxylation of testosterone, was diminished to 74.8% of the control after 5-day treatment with CP-101,606, though no change in the CYP2B protein or CYP2B1 and CYP2B2 mRNA levels were observed ( Figure 3). The CYP2B activity diminished by 5-day treatment returned to the control value after a 3 week-treatment with CP-101,606.

The Effect of CP-101,606 on the CYP2C6 Activity and Expression in Rat Liver After 5-day and 3-week Treatment
The activity of CYP2C6, measured as a rate of the 7-hydroxylation of warfarin, was not significantly changed by 5-day treatment, and only increased (up to 118% of the control value) after 3 weeks of treatment with CP-101,606 ( Figure 4). The CYP2C6 protein or CYP2C6 mRNA level were not changed after short-or long-term treatment with the investigated compound.

The Effect of CP-101,606 on the CYP2C6 Activity and Expression in Rat Liver after 5-Day and 3-Week Treatment
The activity of CYP2C6, measured as a rate of the 7-hydroxylation of warfarin, was not significantly changed by 5-day treatment, and only increased (up to 118% of the control value) after 3 weeks of treatment with CP-101,606 ( Figure 4). The CYP2C6 protein or CYP2C6 mRNA level were not changed after short-or long-term treatment with the investigated compound.

The Effect of CP-101,606 on the CYP2C11 Activity and Expression in Rat Liver After 5-day and 3-week Treatment
The activity of CYP2C11, tested as a rate of the 2-α-or 16-α-hydroxylation of testosterone, was reduced to 76.7% and 60.9% of the control value, respectively, after 5-day treatment with CP-101,606 ( Figure 5). The CYP2C11 protein level was also significantly lowered compared to the control (down to 69% of the control value). Accordingly, the CYP2C11 mRNA level significantly decreased after 5-day treatment with CP-101,606. The reduced activity of CYP2C11 by 5-day treatment returned to the control value after 3 weeks of treatment with CP-101,606.  The activity of CYP2C11, tested as a rate of the 2-α-or 16-α-hydroxylation of testosterone, was reduced to 76.7% and 60.9% of the control value, respectively, after 5-day treatment with CP-101,606 ( Figure 5). The CYP2C11 protein level was also significantly lowered compared to the control (down to 69% of the control value). Accordingly, the CYP2C11 mRNA level significantly decreased after 5-day treatment with CP-101,606. The reduced activity of CYP2C11 by 5-day treatment returned to the control value after 3 weeks of treatment with CP-101,606.

The Effect of CP-101,606 on the CYP3A Activity and Expression in Rat Liver After 5-day and 3-week Treatment
The CYP3A activity, determined as the rate of the 2-β-or 6-β-hydroxylation of testosterone, decreased to 77% and 79.8% of the control value, respectively, after 5-day treatment with CP-101,606 ( Figure 6). The protein level of CYP3A1 was also significantly reduced compared to the control (down to 58% of the control value) and the CYP3A1 mRNA level decreased as well after 5-day treatment. The decreased CYP3A activity (down to 61% and 73% of the control) and CYP3A1 protein level (down to 60% of the control) were still maintained after 3 weeks of treatment with CP-101,606, though the CYP3A1/2 mRNA level remained unchanged.  The CYP3A activity, determined as the rate of the 2-β-or 6-β-hydroxylation of testosterone, decreased to 77% and 79.8% of the control value, respectively, after 5-day treatment with CP-101,606 ( Figure 6). The protein level of CYP3A1 was also significantly reduced compared to the control (down to 58% of the control value) and the CYP3A1 mRNA level decreased as well after 5-day treatment. The decreased CYP3A activity (down to 61% and 73% of the control) and CYP3A1 protein level (down to 60% of the control) were still maintained after 3 weeks of treatment with CP-101,606, though the CYP3A1/2 mRNA level remained unchanged. Figure 6. The effect of a 5-day or 3-week administration of a selective NMDA receptor GluN2B subunit antagonist (CP-101,606) on the cytochrome P450 3A (CYP3A) enzyme activity assessed as the rate of testosterone 2-β-and 6-β-hydroxylation (A), protein level (B) and mRNA (C). All values are shown as the mean ± S.E.M. Student's t-test: *p < 0.05, compared to the control (CON). The representative results of the Western immunoblot analysis (CYP3A1 and CYP3A2 protein bands) are shown in Figure 7.
The representative CYP protein bands in CP-101,606-treated rats, obtained as a result of the Western immunoblot analysis, are shown in Figure 7A (5-day treatment) and Figure  7B (3-week treatment).

The Effect of CP-101,606 on Pituitary and Serum Hormone Levels
After 5-day treatment with CP-101,606, the level of growth hormone-releasing hormone (GHRH) in the pituitary was significantly lower compared to control animals (Figure 8A). At the same time, the serum concentration of growth hormone (GH) and corticosterone (CRT) declined, while the levels of the thyroid hormones (T3 and T4) and interleukin 6 (IL-6) were unaffected.
After 3-week treatment, a gentle diminution in the serum concentration of corticosterone was still maintained, while that of GH returned to the control value ( Figure 8B). The representative CYP protein bands in CP-101,606-treated rats, obtained as a result of the Western immunoblot analysis, are shown in Figure 7A (5-day treatment) and Figure 7B (3-week treatment).

The Effect of CP-101,606 on Pituitary and Serum Hormone Levels
After 5-day treatment with CP-101,606, the level of growth hormone-releasing hormone (GHRH) in the pituitary was significantly lower compared to control animals ( Figure 8A). At the same time, the serum concentration of growth hormone (GH) and corticosterone (CRT) declined, while the levels of the thyroid hormones (T 3 and T 4 ) and interleukin 6 (IL-6) were unaffected.

Discussion
A possible role of the neuroendocrine regulation of cytochrome P450 expression involving the glutamatergic system has not yet been studied. Our study indicates that apart from the brain monoaminergic systems, the brain glutamatergic system may also affect the cytochrome P450 expression and activity via NMDA receptors and endocrine mechanisms.
After 3-week treatment, a gentle diminution in the serum concentration of corticosterone was still maintained, while that of GH returned to the control value ( Figure 8B).

Discussion
A possible role of the neuroendocrine regulation of cytochrome P450 expression involving the glutamatergic system has not yet been studied. Our study indicates that apart from the brain monoaminergic systems, the brain glutamatergic system may also affect the cytochrome P450 expression and activity via NMDA receptors and endocrine mechanisms. CP-101,606, a selective NMDA receptor GluN2B subunit antagonist, produced a lot of changes in the activities of cytochrome P450 enzymes in rat liver after 5-day treatment, as summarized in Table 1.  A decrease in the activity of CYP1A, 2A, 2B, 2C11 and 3A, but not in CYP2C6 was observed. The investigated CYP isoforms are regulated by hormones, such as growth hormone (GH), glucocorticoids (corticosterone) and thyroid hormones (triiodothyronine T3 and thyroxine T4) and via activation of the respective membrane, cytoplasmic or nuclear receptors, in this way regulating the transcription of CYP genes [40][41][42][43][44][45][46].
The detailed analysis of the influence of glutamate receptor agonists and antagonists on GH release has shown that glutamate can elicit prominent and dual regulatory responses on GH secretion, involving a predominantly stimulatory effect via ionotropic receptors, as well as a minor inhibitory effect via metabotropic receptors [28]. Thus, the activation of NMDA receptors resulted in the stimulation of GH secretion; however, the stimulus did not originate in the pituitary, but was generated at the level of GHRH and/or somatostatin neurons. In accordance with the abovementioned neuroendocrine pathway, a decrease in the GHRH level and GH-related expression (mRNA and protein) and activity of CYP2C11 in male rat liver was observed after a 5-day treatment with the selective NMDA receptor GluN2B subunit antagonist CP-101,606 in our experiment. GH is the main regulator of CYP2C11, as well as one of the regulators of other CYP enzymes [40], and our previous studies indicated a positive correlation between the activities of CYP2C11 and CYP3A on the one hand, and the serum GH concentration on the other in male rats [6]. Alternatively, an interplay of the glutamatergic system with other neuroendocrine regulators of GH release, such as the monoamine neurotransmitters dopamine, noradrenaline or serotonin seems also possible. NMDA receptors were shown to be present on catecholaminergic and indoleaminergic neurons and to affect the function of the monoaminergic systems in the brain [47,48]. An important role of the mentioned monoaminergic systems in the GH regulation has been documented [4,5,13,49]. On the other hand, the expression of CYP2C6 enzyme, which is less susceptible to neuroendocrine regulation, was not affected by a 5-day treatment with the investigated compound.   A decrease in the activity of CYP1A, 2A, 2B, 2C11 and 3A, but not in CYP2C6 was observed. The investigated CYP isoforms are regulated by hormones, such as growth hormone (GH), glucocorticoids (corticosterone) and thyroid hormones (triiodothyronine T3 and thyroxine T4) and via activation of the respective membrane, cytoplasmic or nuclear receptors, in this way regulating the transcription of CYP genes [40][41][42][43][44][45][46].
The detailed analysis of the influence of glutamate receptor agonists and antagonists on GH release has shown that glutamate can elicit prominent and dual regulatory responses on GH secretion, involving a predominantly stimulatory effect via ionotropic receptors, as well as a minor inhibitory effect via metabotropic receptors [28]. Thus, the activation of NMDA receptors resulted in the stimulation of GH secretion; however, the stimulus did not originate in the pituitary, but was generated at the level of GHRH and/or somatostatin neurons. In accordance with the abovementioned neuroendocrine pathway, a decrease in the GHRH level and GH-related expression (mRNA and protein) and activity of CYP2C11 in male rat liver was observed after a 5-day treatment with the selective NMDA receptor GluN2B subunit antagonist CP-101,606 in our experiment. GH is the main regulator of CYP2C11, as well as one of the regulators of other CYP enzymes [40], and our previous studies indicated a positive correlation between the activities of CYP2C11 and CYP3A on the one hand, and the serum GH concentration on the other in male rats [6]. Alternatively, an interplay of the glutamatergic system with other neuroendocrine regulators of GH release, such as the monoamine neurotransmitters dopamine, noradrenaline or serotonin seems also possible. NMDA receptors were shown to be present on catecholaminergic and indoleaminergic neurons and to affect the function of the monoaminergic systems in the brain [47,48]. An important role of the mentioned monoaminergic systems in the GH regulation has been documented [4,5,13,49]. On the other hand, the expression of CYP2C6 enzyme, which is less susceptible to neuroendocrine regulation, was not affected by a 5-day treatment with the investigated compound.  A decrease in the activity of CYP1A, 2A, 2B, 2C11 and 3A, but not in CYP2C6 was observed. The investigated CYP isoforms are regulated by hormones, such as growth hormone (GH), glucocorticoids (corticosterone) and thyroid hormones (triiodothyronine T3 and thyroxine T4) and via activation of the respective membrane, cytoplasmic or nuclear receptors, in this way regulating the transcription of CYP genes [40][41][42][43][44][45][46].
The detailed analysis of the influence of glutamate receptor agonists and antagonists on GH release has shown that glutamate can elicit prominent and dual regulatory responses on GH secretion, involving a predominantly stimulatory effect via ionotropic receptors, as well as a minor inhibitory effect via metabotropic receptors [28]. Thus, the activation of NMDA receptors resulted in the stimulation of GH secretion; however, the stimulus did not originate in the pituitary, but was generated at the level of GHRH and/or somatostatin neurons. In accordance with the abovementioned neuroendocrine pathway, a decrease in the GHRH level and GH-related expression (mRNA and protein) and activity of CYP2C11 in male rat liver was observed after a 5-day treatment with the selective NMDA receptor GluN2B subunit antagonist CP-101,606 in our experiment. GH is the main regulator of CYP2C11, as well as one of the regulators of other CYP enzymes [40], and our previous studies indicated a positive correlation between the activities of CYP2C11 and CYP3A on the one hand, and the serum GH concentration on the other in male rats [6]. Alternatively, an interplay of the glutamatergic system with other neuroendocrine regulators of GH release, such as the monoamine neurotransmitters dopamine, noradrenaline or serotonin seems also possible. NMDA receptors were shown to be present on catecholaminergic and indoleaminergic neurons and to affect the function of the monoaminergic systems in the brain [47,48]. An important role of the mentioned monoaminergic systems in the GH regulation has been documented [4,5,13,49]. On the other hand, the expression of CYP2C6 enzyme, which is less susceptible to neuroendocrine regulation, was not affected by a 5-day treatment with the investigated compound. A decrease in the activity of CYP1A, 2A, 2B, 2C11 and 3A, but not in CYP2C6 was observed. The investigated CYP isoforms are regulated by hormones, such as growth hormone (GH), glucocorticoids (corticosterone) and thyroid hormones (triiodothyronine T3 and thyroxine T4) and via activation of the respective membrane, cytoplasmic or nuclear receptors, in this way regulating the transcription of CYP genes [40][41][42][43][44][45][46].

days 3 weeks
The detailed analysis of the influence of glutamate receptor agonists and antagonists on GH release has shown that glutamate can elicit prominent and dual regulatory responses on GH secretion, involving a predominantly stimulatory effect via ionotropic receptors, as well as a minor inhibitory effect via metabotropic receptors [28]. Thus, the activation of NMDA receptors resulted in the stimulation of GH secretion; however, the stimulus did not originate in the pituitary, but was generated at the level of GHRH and/or somatostatin neurons. In accordance with the abovementioned neuroendocrine pathway, a decrease in the GHRH level and GH-related expression (mRNA and protein) and activity of CYP2C11 in male rat liver was observed after a 5-day treatment with the selective NMDA receptor GluN2B subunit antagonist CP-101,606 in our experiment. GH is the main regulator of CYP2C11, as well as one of the regulators of other CYP enzymes [40], and our previous studies indicated a positive correlation between the activities of CYP2C11 and CYP3A on the one hand, and the serum GH concentration on the other in male rats [6]. Alternatively, an interplay of the glutamatergic system with other neuroendocrine regulators of GH release, such as the monoamine neurotransmitters dopamine, noradrenaline or serotonin seems also possible. NMDA receptors were shown to be present on catecholaminergic and indoleaminergic neurons and to affect the function of the monoaminergic systems in the brain [47,48]. An important role of the mentioned monoaminergic systems in the GH regulation has been documented [4,5,13,49]. On the other hand, the expression of CYP2C6 enzyme, which is less susceptible to neuroendocrine regulation, was not affected by a 5-day treatment with the investigated compound. A decrease in the activity of CYP1A, 2A, 2B, 2C11 and 3A, but not in CYP2C6 was observed. The investigated CYP isoforms are regulated by hormones, such as growth hormone (GH), glucocorticoids (corticosterone) and thyroid hormones (triiodothyronine T3 and thyroxine T4) and via activation of the respective membrane, cytoplasmic or nuclear receptors, in this way regulating the transcription of CYP genes [40][41][42][43][44][45][46].

days 3 weeks
The detailed analysis of the influence of glutamate receptor agonists and antagonists on GH release has shown that glutamate can elicit prominent and dual regulatory responses on GH secretion, involving a predominantly stimulatory effect via ionotropic receptors, as well as a minor inhibitory effect via metabotropic receptors [28]. Thus, the activation of NMDA receptors resulted in the stimulation of GH secretion; however, the stimulus did not originate in the pituitary, but was generated at the level of GHRH and/or somatostatin neurons. In accordance with the abovementioned neuroendocrine pathway, a decrease in the GHRH level and GH-related expression (mRNA and protein) and activity of CYP2C11 in male rat liver was observed after a 5-day treatment with the selective NMDA receptor GluN2B subunit antagonist CP-101,606 in our experiment. GH is the main regulator of CYP2C11, as well as one of the regulators of other CYP enzymes [40], and our previous studies indicated a positive correlation between the activities of CYP2C11 and CYP3A on the one hand, and the serum GH concentration on the other in male rats [6]. Alternatively, an interplay of the glutamatergic system with other neuroendocrine regulators of GH release, such as the monoamine neurotransmitters dopamine, noradrenaline or serotonin seems also possible. NMDA receptors were shown to be present on catecholaminergic and indoleaminergic neurons and to affect the function of the monoaminergic systems in the brain [47,48]. An important role of the mentioned monoaminergic systems in the GH regulation has been documented [4,5,13,49]. On the other hand, the expression of CYP2C6 enzyme, which is less susceptible to neuroendocrine regulation, was not affected by a 5-day treatment with the investigated compound.

days 3 weeks
activity protein mRNA activity protein mRNA

A1/2
Pharmaceutics 2021, 13, x  A decrease in the activity of CYP1A, 2A, 2B, 2C11 and 3A, but n observed. The investigated CYP isoforms are regulated by hormones, s mone (GH), glucocorticoids (corticosterone) and thyroid hormones ( and thyroxine T4) and via activation of the respective membrane, cyto receptors, in this way regulating the transcription of CYP genes [40][41][42][43][44][45][46] The detailed analysis of the influence of glutamate receptor agoni on GH release has shown that glutamate can elicit prominent and sponses on GH secretion, involving a predominantly stimulatory effec ceptors, as well as a minor inhibitory effect via metabotropic receptor tivation of NMDA receptors resulted in the stimulation of GH secre stimulus did not originate in the pituitary, but was generated at the lev somatostatin neurons. In accordance with the abovementioned neuroe a decrease in the GHRH level and GH-related expression (mRNA and ity of CYP2C11 in male rat liver was observed after a 5-day treatmen NMDA receptor GluN2B subunit antagonist CP-101,606 in our exp main regulator of CYP2C11, as well as one of the regulators of other and our previous studies indicated a positive correlation betwee CYP2C11 and CYP3A on the one hand, and the serum GH concentra male rats [6]. Alternatively, an interplay of the glutamatergic system w docrine regulators of GH release, such as the monoamine neurotran noradrenaline or serotonin seems also possible. NMDA receptors wer sent on catecholaminergic and indoleaminergic neurons and to affect monoaminergic systems in the brain [47,48]. An important role of the aminergic systems in the GH regulation has been documented [4,5,1 hand, the expression of CYP2C6 enzyme, which is less susceptible to n ulation, was not affected by a 5-day treatment with the investigated co CYPs 5 days 3 wee activity protein mRNA activity prote

3A1/2
Pharmaceutics 2021, 13, x   Table 1. Summary of the effects of the 5-day and 3-w sion and activity of liver cytochrome P450 enzymes.
↑, ↓ increase or decrease, respectively; − no change; n A decrease in the activity of CYP1A, 2A, 2 observed. The investigated CYP isoforms are reg mone (GH), glucocorticoids (corticosterone) an and thyroxine T4) and via activation of the resp receptors, in this way regulating the transcriptio The detailed analysis of the influence of glu on GH release has shown that glutamate can sponses on GH secretion, involving a predomin ceptors, as well as a minor inhibitory effect via tivation of NMDA receptors resulted in the st stimulus did not originate in the pituitary, but w somatostatin neurons. In accordance with the ab a decrease in the GHRH level and GH-related e ity of CYP2C11 in male rat liver was observed NMDA receptor GluN2B subunit antagonist C main regulator of CYP2C11, as well as one of th and our previous studies indicated a positiv CYP2C11 and CYP3A on the one hand, and the male rats [6]. Alternatively, an interplay of the g docrine regulators of GH release, such as the m noradrenaline or serotonin seems also possible. sent on catecholaminergic and indoleaminergic monoaminergic systems in the brain [47,48]. An aminergic systems in the GH regulation has be hand, the expression of CYP2C6 enzyme, which ulation, was not affected by a 5-day treatment w CYPs 5 days activity protein mRNA ac n.t.

3A1/2
Pharmaceutics 2021, 13, x  A decrease in the activity of observed. The investigated CYP is mone (GH), glucocorticoids (corti and thyroxine T4) and via activati receptors, in this way regulating t The detailed analysis of the in on GH release has shown that g sponses on GH secretion, involvin ceptors, as well as a minor inhibit tivation of NMDA receptors resu stimulus did not originate in the p somatostatin neurons. In accordan a decrease in the GHRH level and ity of CYP2C11 in male rat liver w NMDA receptor GluN2B subuni main regulator of CYP2C11, as w and our previous studies indica CYP2C11 and CYP3A on the one male rats [6]. Alternatively, an int docrine regulators of GH release, noradrenaline or serotonin seems sent on catecholaminergic and ind monoaminergic systems in the br aminergic systems in the GH reg hand, the expression of CYP2C6 e ulation, was not affected by a 5-da  A decrease in the activity of CYP1A, 2A, 2B, 2C11 and 3A, but not in CYP2C6 was observed. The investigated CYP isoforms are regulated by hormones, such as growth hormone (GH), glucocorticoids (corticosterone) and thyroid hormones (triiodothyronine T3 and thyroxine T4) and via activation of the respective membrane, cytoplasmic or nuclear receptors, in this way regulating the transcription of CYP genes [40][41][42][43][44][45][46].
The detailed analysis of the influence of glutamate receptor agonists and antagonists on GH release has shown that glutamate can elicit prominent and dual regulatory responses on GH secretion, involving a predominantly stimulatory effect via ionotropic receptors, as well as a minor inhibitory effect via metabotropic receptors [28]. Thus, the activation of NMDA receptors resulted in the stimulation of GH secretion; however, the stimulus did not originate in the pituitary, but was generated at the level of GHRH and/or somatostatin neurons. In accordance with the abovementioned neuroendocrine pathway, a decrease in the GHRH level and GH-related expression (mRNA and protein) and activity of CYP2C11 in male rat liver was observed after a 5-day treatment with the selective NMDA receptor GluN2B subunit antagonist CP-101,606 in our experiment. GH is the main regulator of CYP2C11, as well as one of the regulators of other CYP enzymes [40], and our previous studies indicated a positive correlation between the activities of CYP2C11 and CYP3A on the one hand, and the serum GH concentration on the other in male rats [6]. Alternatively, an interplay of the glutamatergic system with other neuroendocrine regulators of GH release, such as the monoamine neurotransmitters dopamine, noradrenaline or serotonin seems also possible. NMDA receptors were shown to be present on catecholaminergic and indoleaminergic neurons and to affect the function of the monoaminergic systems in the brain [47,48]. An important role of the mentioned monoaminergic systems in the GH regulation has been documented [4,5,13,49]. On the other hand, the expression of CYP2C6 enzyme, which is less susceptible to neuroendocrine regulation, was not affected by a 5-day treatment with the investigated compound.

days 3 weeks
activity protein mRNA activity protein mRNA
The detailed analysis of the influence of glutamate receptor agonists and antagonists on GH release has shown that glutamate can elicit prominent and dual regulatory responses on GH secretion, involving a predominantly stimulatory effect via ionotropic receptors, as well as a minor inhibitory effect via metabotropic receptors [28]. Thus, the activation of NMDA receptors resulted in the stimulation of GH secretion; however, the stimulus did not originate in the pituitary, but was generated at the level of GHRH and/or somatostatin neurons. In accordance with the abovementioned neuroendocrine pathway, a decrease in the GHRH level and GH-related expression (mRNA and protein) and activity of CYP2C11 in male rat liver was observed after a 5-day treatment with the selective NMDA receptor GluN2B subunit antagonist CP-101,606 in our experiment. GH is the main regulator of CYP2C11, as well as one of the regulators of other CYP enzymes [40], and our previous studies indicated a positive correlation between the activities of CYP2C11 and CYP3A on the one hand, and the serum GH concentration on the other in male rats [6]. Alternatively, an interplay of the glutamatergic system with other neuroendocrine regulators of GH release, such as the monoamine neurotransmitters dopamine, noradrenaline or serotonin seems also possible. NMDA receptors were shown to be present on catecholaminergic and indoleaminergic neurons and to affect the function of the monoaminergic systems in the brain [47,48]. An important role of the mentioned monoaminergic systems in the GH regulation has been documented [4,5,13,49]. On the other hand, the expression of CYP2C6 enzyme, which is less susceptible to neuroendocrine regulation, was not affected by a 5-day treatment with the investigated compound.

days 3 weeks
activity protein mRNA activity protein mRNA
The detailed analysis of the influence of glutamate receptor agonists and antagonists on GH release has shown that glutamate can elicit prominent and dual regulatory responses on GH secretion, involving a predominantly stimulatory effect via ionotropic receptors, as well as a minor inhibitory effect via metabotropic receptors [28]. Thus, the activation of NMDA receptors resulted in the stimulation of GH secretion; however, the stimulus did not originate in the pituitary, but was generated at the level of GHRH and/or somatostatin neurons. In accordance with the abovementioned neuroendocrine pathway, a decrease in the GHRH level and GH-related expression (mRNA and protein) and activity of CYP2C11 in male rat liver was observed after a 5-day treatment with the selective NMDA receptor GluN2B subunit antagonist CP-101,606 in our experiment. GH is the main regulator of CYP2C11, as well as one of the regulators of other CYP enzymes [40], and our previous studies indicated a positive correlation between the activities of CYP2C11 and CYP3A on the one hand, and the serum GH concentration on the other in male rats [6]. Alternatively, an interplay of the glutamatergic system with other neuroendocrine regulators of GH release, such as the monoamine neurotransmitters dopamine, noradrenaline or serotonin seems also possible. NMDA receptors were shown to be present on catecholaminergic and indoleaminergic neurons and to affect the function of the monoaminergic systems in the brain [47,48]. An important role of the mentioned monoaminergic systems in the GH regulation has been documented [4,5,13,49]. On the other hand, the expression of CYP2C6 enzyme, which is less susceptible to neuroendocrine regulation, was not affected by a 5-day treatment with the investigated compound.  A decrease in the activity of CYP1A, 2A, 2B, 2C11 and 3A, but not in CYP2C6 was observed. The investigated CYP isoforms are regulated by hormones, such as growth hormone (GH), glucocorticoids (corticosterone) and thyroid hormones (triiodothyronine T3 and thyroxine T4) and via activation of the respective membrane, cytoplasmic or nuclear receptors, in this way regulating the transcription of CYP genes [40][41][42][43][44][45][46].

CYPs
The detailed analysis of the influence of glutamate receptor agonists and antagonists on GH release has shown that glutamate can elicit prominent and dual regulatory responses on GH secretion, involving a predominantly stimulatory effect via ionotropic receptors, as well as a minor inhibitory effect via metabotropic receptors [28]. Thus, the activation of NMDA receptors resulted in the stimulation of GH secretion; however, the stimulus did not originate in the pituitary, but was generated at the level of GHRH and/or somatostatin neurons. In accordance with the abovementioned neuroendocrine pathway, a decrease in the GHRH level and GH-related expression (mRNA and protein) and activity of CYP2C11 in male rat liver was observed after a 5-day treatment with the selective NMDA receptor GluN2B subunit antagonist CP-101,606 in our experiment. GH is the main regulator of CYP2C11, as well as one of the regulators of other CYP enzymes [40], and our previous studies indicated a positive correlation between the activities of CYP2C11 and CYP3A on the one hand, and the serum GH concentration on the other in male rats [6]. Alternatively, an interplay of the glutamatergic system with other neuroendocrine regulators of GH release, such as the monoamine neurotransmitters dopamine, noradrenaline or serotonin seems also possible. NMDA receptors were shown to be present on catecholaminergic and indoleaminergic neurons and to affect the function of the monoaminergic systems in the brain [47,48]. An important role of the mentioned monoaminergic systems in the GH regulation has been documented [4,5,13,49]. On the other hand, the expression of CYP2C6 enzyme, which is less susceptible to neuroendocrine regulation, was not affected by a 5-day treatment with the investigated compound.  A decrease in the activity of CYP1A, 2A, 2B, 2C11 and 3A, but not in CYP2C6 was observed. The investigated CYP isoforms are regulated by hormones, such as growth hormone (GH), glucocorticoids (corticosterone) and thyroid hormones (triiodothyronine T3 and thyroxine T4) and via activation of the respective membrane, cytoplasmic or nuclear receptors, in this way regulating the transcription of CYP genes [40][41][42][43][44][45][46].

CYPs
The detailed analysis of the influence of glutamate receptor agonists and antagonists on GH release has shown that glutamate can elicit prominent and dual regulatory responses on GH secretion, involving a predominantly stimulatory effect via ionotropic receptors, as well as a minor inhibitory effect via metabotropic receptors [28]. Thus, the activation of NMDA receptors resulted in the stimulation of GH secretion; however, the stimulus did not originate in the pituitary, but was generated at the level of GHRH and/or somatostatin neurons. In accordance with the abovementioned neuroendocrine pathway, a decrease in the GHRH level and GH-related expression (mRNA and protein) and activity of CYP2C11 in male rat liver was observed after a 5-day treatment with the selective NMDA receptor GluN2B subunit antagonist CP-101,606 in our experiment. GH is the main regulator of CYP2C11, as well as one of the regulators of other CYP enzymes [40], and our previous studies indicated a positive correlation between the activities of CYP2C11 and CYP3A on the one hand, and the serum GH concentration on the other in male rats [6]. Alternatively, an interplay of the glutamatergic system with other neuroendocrine regulators of GH release, such as the monoamine neurotransmitters dopamine, noradrenaline or serotonin seems also possible. NMDA receptors were shown to be present on catecholaminergic and indoleaminergic neurons and to affect the function of the monoaminergic systems in the brain [47,48]. An important role of the mentioned monoaminergic systems in the GH regulation has been documented [4,5,13,49]. On the other hand, the expression of CYP2C6 enzyme, which is less susceptible to neuroendocrine regulation, was not affected by a 5-day treatment with the investigated compound. A decrease in the activity of CYP1A, 2A, 2B, 2C11 and 3A, but not in CYP2C6 was observed. The investigated CYP isoforms are regulated by hormones, such as growth hormone (GH), glucocorticoids (corticosterone) and thyroid hormones (triiodothyronine T3 and thyroxine T4) and via activation of the respective membrane, cytoplasmic or nuclear receptors, in this way regulating the transcription of CYP genes [40][41][42][43][44][45][46].

CYPs
The detailed analysis of the influence of glutamate receptor agonists and antagonists on GH release has shown that glutamate can elicit prominent and dual regulatory responses on GH secretion, involving a predominantly stimulatory effect via ionotropic receptors, as well as a minor inhibitory effect via metabotropic receptors [28]. Thus, the activation of NMDA receptors resulted in the stimulation of GH secretion; however, the stimulus did not originate in the pituitary, but was generated at the level of GHRH and/or somatostatin neurons. In accordance with the abovementioned neuroendocrine pathway, a decrease in the GHRH level and GH-related expression (mRNA and protein) and activity of CYP2C11 in male rat liver was observed after a 5-day treatment with the selective NMDA receptor GluN2B subunit antagonist CP-101,606 in our experiment. GH is the main regulator of CYP2C11, as well as one of the regulators of other CYP enzymes [40], and our previous studies indicated a positive correlation between the activities of CYP2C11 and CYP3A on the one hand, and the serum GH concentration on the other in male rats [6]. Alternatively, an interplay of the glutamatergic system with other neuroendocrine regulators of GH release, such as the monoamine neurotransmitters dopamine, noradrenaline or serotonin seems also possible. NMDA receptors were shown to be present on catecholaminergic and indoleaminergic neurons and to affect the function of the monoaminergic systems in the brain [47,48]. An important role of the mentioned monoaminergic systems in the GH regulation has been documented [ A decrease in the activity of CYP1A, 2A, 2B, 2C11 and 3A, but not in CYP2C6 was observed. The investigated CYP isoforms are regulated by hormones, such as growth hormone (GH), glucocorticoids (corticosterone) and thyroid hormones (triiodothyronine T3 and thyroxine T4) and via activation of the respective membrane, cytoplasmic or nuclear receptors, in this way regulating the transcription of CYP genes [40][41][42][43][44][45][46].
The detailed analysis of the influence of glutamate receptor agonists and antagonists on GH release has shown that glutamate can elicit prominent and dual regulatory responses on GH secretion, involving a predominantly stimulatory effect via ionotropic receptors, as well as a minor inhibitory effect via metabotropic receptors [28]. Thus, the activation of NMDA receptors resulted in the stimulation of GH secretion; however, the stimulus did not originate in the pituitary, but was generated at the level of GHRH and/or somatostatin neurons. In accordance with the abovementioned neuroendocrine pathway, a decrease in the GHRH level and GH-related expression (mRNA and protein) and activity of CYP2C11 in male rat liver was observed after a 5-day treatment with the selective NMDA receptor GluN2B subunit antagonist CP-101,606 in our experiment. GH is the main regulator of CYP2C11, as well as one of the regulators of other CYP enzymes [40], and our previous studies indicated a positive correlation between the activities of CYP2C11 and CYP3A on the one hand, and the serum GH concentration on the other in male rats [6]. Alternatively, an interplay of the glutamatergic system with other neuroendocrine regulators of GH release, such as the monoamine neurotransmitters dopamine, noradrenaline or serotonin seems also possible. NMDA receptors were shown to be present on catecholaminergic and indoleaminergic neurons and to affect the function of the monoaminergic systems in the brain [47,48]. An important role of the mentioned monoaminergic systems in the GH regulation has been documented [4,5,13,49]. On the other hand, the expression of CYP2C6 enzyme, which is less susceptible to neuroendocrine regulation, was not affected by a 5-day treatment with the investigated compound. A decrease in the activity of CYP1A, 2A, 2B, 2C11 and 3A, but not in CYP2C6 was observed. The investigated CYP isoforms are regulated by hormones, such as growth hormone (GH), glucocorticoids (corticosterone) and thyroid hormones (triiodothyronine T3 and thyroxine T4) and via activation of the respective membrane, cytoplasmic or nuclear receptors, in this way regulating the transcription of CYP genes [40][41][42][43][44][45][46].

CYPs
The detailed analysis of the influence of glutamate receptor agonists and antagonists on GH release has shown that glutamate can elicit prominent and dual regulatory responses on GH secretion, involving a predominantly stimulatory effect via ionotropic receptors, as well as a minor inhibitory effect via metabotropic receptors [28]. Thus, the activation of NMDA receptors resulted in the stimulation of GH secretion; however, the stimulus did not originate in the pituitary, but was generated at the level of GHRH and/or somatostatin neurons. In accordance with the abovementioned neuroendocrine pathway, a decrease in the GHRH level and GH-related expression (mRNA and protein) and activity of CYP2C11 in male rat liver was observed after a 5-day treatment with the selective NMDA receptor GluN2B subunit antagonist CP-101,606 in our experiment. GH is the main regulator of CYP2C11, as well as one of the regulators of other CYP enzymes [40], and our previous studies indicated a positive correlation between the activities of CYP2C11 and CYP3A on the one hand, and the serum GH concentration on the other in male rats [6]. Alternatively, an interplay of the glutamatergic system with other neuroendocrine regulators of GH release, such as the monoamine neurotransmitters dopamine, noradrenaline or serotonin seems also possible. NMDA receptors were shown to be present on catecholaminergic and indoleaminergic neurons and to affect the function of the monoaminergic systems in the brain [47,48]. An important role of the mentioned monoaminergic systems in the GH regulation has been documented [4,5,13,49]. On the other hand, the expression of CYP2C6 enzyme, which is less susceptible to neuroendocrine regulation, was not affected by a 5-day treatment with the investigated compound. A decrease in the activity of CYP1A, 2A, 2B, 2C11 and 3A, but not in CYP2C6 was observed. The investigated CYP isoforms are regulated by hormones, such as growth hormone (GH), glucocorticoids (corticosterone) and thyroid hormones (triiodothyronine T3 and thyroxine T4) and via activation of the respective membrane, cytoplasmic or nuclear receptors, in this way regulating the transcription of CYP genes [40][41][42][43][44][45][46].

CYPs
The detailed analysis of the influence of glutamate receptor agonists and antagonists on GH release has shown that glutamate can elicit prominent and dual regulatory responses on GH secretion, involving a predominantly stimulatory effect via ionotropic receptors, as well as a minor inhibitory effect via metabotropic receptors [28]. Thus, the activation of NMDA receptors resulted in the stimulation of GH secretion; however, the stimulus did not originate in the pituitary, but was generated at the level of GHRH and/or somatostatin neurons. In accordance with the abovementioned neuroendocrine pathway, a decrease in the GHRH level and GH-related expression (mRNA and protein) and activity of CYP2C11 in male rat liver was observed after a 5-day treatment with the selective NMDA receptor GluN2B subunit antagonist CP-101,606 in our experiment. GH is the main regulator of CYP2C11, as well as one of the regulators of other CYP enzymes [40], and our previous studies indicated a positive correlation between the activities of CYP2C11 and CYP3A on the one hand, and the serum GH concentration on the other in male rats [6]. Alternatively, an interplay of the glutamatergic system with other neuroendocrine regulators of GH release, such as the monoamine neurotransmitters dopamine, noradrenaline or serotonin seems also possible. NMDA receptors were shown to be present on catecholaminergic and indoleaminergic neurons and to affect the function of the monoaminergic systems in the brain [47,48]. An important role of the mentioned monoaminergic systems in the GH regulation has been documented [4,5,13,49]. On the other hand, the expression of CYP2C6 enzyme, which is less susceptible to neuroendocrine regulation, was not affected by a 5-day treatment with the investigated compound. A decrease in the activity of CYP1A, 2A, 2B, 2C11 and 3A, but not in CYP2C6 was observed. The investigated CYP isoforms are regulated by hormones, such as growth hormone (GH), glucocorticoids (corticosterone) and thyroid hormones (triiodothyronine T3 and thyroxine T4) and via activation of the respective membrane, cytoplasmic or nuclear receptors, in this way regulating the transcription of CYP genes [40][41][42][43][44][45][46].

CYPs
The detailed analysis of the influence of glutamate receptor agonists and antagonists on GH release has shown that glutamate can elicit prominent and dual regulatory responses on GH secretion, involving a predominantly stimulatory effect via ionotropic receptors, as well as a minor inhibitory effect via metabotropic receptors [28]. Thus, the activation of NMDA receptors resulted in the stimulation of GH secretion; however, the stimulus did not originate in the pituitary, but was generated at the level of GHRH and/or somatostatin neurons. In accordance with the abovementioned neuroendocrine pathway, a decrease in the GHRH level and GH-related expression (mRNA and protein) and activity of CYP2C11 in male rat liver was observed after a 5-day treatment with the selective NMDA receptor GluN2B subunit antagonist CP-101,606 in our experiment. GH is the main regulator of CYP2C11, as well as one of the regulators of other CYP enzymes [40], and our previous studies indicated a positive correlation between the activities of CYP2C11 and CYP3A on the one hand, and the serum GH concentration on the other in male rats [6]. Alternatively, an interplay of the glutamatergic system with other neuroendocrine regulators of GH release, such as the monoamine neurotransmitters dopamine, noradrenaline or serotonin seems also possible. NMDA receptors were shown to be present on catecholaminergic and indoleaminergic neurons and to affect the function of the monoaminergic systems in the brain [47,48]. An important role of the mentioned monoaminergic systems in the GH regulation has been documented [4,5,13,49]. On the other hand, the expression of CYP2C6 enzyme, which is less susceptible to neuroendocrine regulation, was not affected by a 5-day treatment with the investigated compound. A decrease in the activity of CYP1A, 2A, 2B, 2C11 and 3A, but not in CYP2C6 was observed. The investigated CYP isoforms are regulated by hormones, such as growth hormone (GH), glucocorticoids (corticosterone) and thyroid hormones (triiodothyronine T3 and thyroxine T4) and via activation of the respective membrane, cytoplasmic or nuclear receptors, in this way regulating the transcription of CYP genes [40][41][42][43][44][45][46].

CYPs
The detailed analysis of the influence of glutamate receptor agonists and antagonists on GH release has shown that glutamate can elicit prominent and dual regulatory responses on GH secretion, involving a predominantly stimulatory effect via ionotropic receptors, as well as a minor inhibitory effect via metabotropic receptors [28]. Thus, the activation of NMDA receptors resulted in the stimulation of GH secretion; however, the stimulus did not originate in the pituitary, but was generated at the level of GHRH and/or somatostatin neurons. In accordance with the abovementioned neuroendocrine pathway, a decrease in the GHRH level and GH-related expression (mRNA and protein) and activity of CYP2C11 in male rat liver was observed after a 5-day treatment with the selective NMDA receptor GluN2B subunit antagonist CP-101,606 in our experiment. GH is the main regulator of CYP2C11, as well as one of the regulators of other CYP enzymes [40], and our previous studies indicated a positive correlation between the activities of CYP2C11 and CYP3A on the one hand, and the serum GH concentration on the other in male rats [6]. Alternatively, an interplay of the glutamatergic system with other neuroendocrine regulators of GH release, such as the monoamine neurotransmitters dopamine, noradrenaline or serotonin seems also possible. NMDA receptors were shown to be present on catecholaminergic and indoleaminergic neurons and to affect the function of the monoaminergic systems in the brain [47,48]. An important role of the mentioned monoaminergic systems in the GH regulation has been documented [4,5,13,49]. On the other hand, the expression of CYP2C6 enzyme, which is less susceptible to neuroendocrine regulation, was not affected by a 5-day treatment with the investigated compound.  A decrease in the activity of CYP1A, 2A, 2B, 2C11 and 3A, but not in CYP2C6 was observed. The investigated CYP isoforms are regulated by hormones, such as growth hormone (GH), glucocorticoids (corticosterone) and thyroid hormones (triiodothyronine T3 and thyroxine T4) and via activation of the respective membrane, cytoplasmic or nuclear receptors, in this way regulating the transcription of CYP genes [40][41][42][43][44][45][46].

days 3 weeks
The detailed analysis of the influence of glutamate receptor agonists and antagonists on GH release has shown that glutamate can elicit prominent and dual regulatory responses on GH secretion, involving a predominantly stimulatory effect via ionotropic receptors, as well as a minor inhibitory effect via metabotropic receptors [28]. Thus, the activation of NMDA receptors resulted in the stimulation of GH secretion; however, the stimulus did not originate in the pituitary, but was generated at the level of GHRH and/or somatostatin neurons. In accordance with the abovementioned neuroendocrine pathway, a decrease in the GHRH level and GH-related expression (mRNA and protein) and activity of CYP2C11 in male rat liver was observed after a 5-day treatment with the selective NMDA receptor GluN2B subunit antagonist CP-101,606 in our experiment. GH is the main regulator of CYP2C11, as well as one of the regulators of other CYP enzymes [40], and our previous studies indicated a positive correlation between the activities of CYP2C11 and CYP3A on the one hand, and the serum GH concentration on the other in male rats [6]. Alternatively, an interplay of the glutamatergic system with other neuroendocrine regulators of GH release, such as the monoamine neurotransmitters dopamine, noradrenaline or serotonin seems also possible. NMDA receptors were shown to be present on catecholaminergic and indoleaminergic neurons and to affect the function of the monoaminergic systems in the brain [47,48]. An important role of the mentioned monoaminergic systems in the GH regulation has been documented [4,5,13,49]. On the other hand, the expression of CYP2C6 enzyme, which is less susceptible to neuroendocrine regulation, was not affected by a 5-day treatment with the investigated compound.

A1/2
Pharmaceutics 2021, 13, x  A decrease in the activity of CYP1A, 2A, 2B, 2C11 and 3A, but n observed. The investigated CYP isoforms are regulated by hormones, s mone (GH), glucocorticoids (corticosterone) and thyroid hormones ( and thyroxine T4) and via activation of the respective membrane, cyto receptors, in this way regulating the transcription of CYP genes [40][41][42][43][44][45][46] The detailed analysis of the influence of glutamate receptor agoni on GH release has shown that glutamate can elicit prominent and sponses on GH secretion, involving a predominantly stimulatory effec ceptors, as well as a minor inhibitory effect via metabotropic receptor tivation of NMDA receptors resulted in the stimulation of GH secre stimulus did not originate in the pituitary, but was generated at the lev somatostatin neurons. In accordance with the abovementioned neuroe a decrease in the GHRH level and GH-related expression (mRNA and ity of CYP2C11 in male rat liver was observed after a 5-day treatmen NMDA receptor GluN2B subunit antagonist CP-101,606 in our exp main regulator of CYP2C11, as well as one of the regulators of other and our previous studies indicated a positive correlation betwee CYP2C11 and CYP3A on the one hand, and the serum GH concentra male rats [6]. Alternatively, an interplay of the glutamatergic system w docrine regulators of GH release, such as the monoamine neurotran noradrenaline or serotonin seems also possible. NMDA receptors wer sent on catecholaminergic and indoleaminergic neurons and to affect monoaminergic systems in the brain [47,48]. An important role of the aminergic systems in the GH regulation has been documented [4,5,1 hand, the expression of CYP2C6 enzyme, which is less susceptible to n ulation, was not affected by a 5-day treatment with the investigated co

3A1/2
Pharmaceutics 2021, 13, x  A decrease in the activity of CYP1A observed. The investigated CYP isoforms mone (GH), glucocorticoids (corticostero and thyroxine T4) and via activation of th receptors, in this way regulating the trans The detailed analysis of the influence on GH release has shown that glutamat sponses on GH secretion, involving a pre ceptors, as well as a minor inhibitory effe tivation of NMDA receptors resulted in stimulus did not originate in the pituitary somatostatin neurons. In accordance with a decrease in the GHRH level and GH-rel ity of CYP2C11 in male rat liver was obs NMDA receptor GluN2B subunit antago main regulator of CYP2C11, as well as on and our previous studies indicated a CYP2C11 and CYP3A on the one hand, a male rats [6]. Alternatively, an interplay o docrine regulators of GH release, such a noradrenaline or serotonin seems also po sent on catecholaminergic and indoleami monoaminergic systems in the brain [47, aminergic systems in the GH regulation hand, the expression of CYP2C6 enzyme, ulation, was not affected by a 5-day treatm  Table 1. Summary of the effects of the 5-day and 3-week treatment with CP-101,606 on the expres-sion and activity of liver cytochrome P450 enzymes.
The detailed analysis of the influence of glutamate receptor agonists and antagonists on GH release has shown that glutamate can elicit prominent and dual regulatory re-sponses on GH secretion, involving a predominantly stimulatory effect via ionotropic re-ceptors, as well as a minor inhibitory effect via metabotropic receptors [28]. Thus, the ac-tivation of NMDA receptors resulted in the stimulation of GH secretion; however, the stimulus did not originate in the pituitary, but was generated at the level of GHRH and/or somatostatin neurons. In accordance with the abovementioned neuroendocrine pathway, a decrease in the GHRH level and GH-related expression (mRNA and protein) and activ-ity of CYP2C11 in male rat liver was observed after a 5-day treatment with the selective NMDA receptor GluN2B subunit antagonist CP-101,606 in our experiment. GH is the main regulator of CYP2C11, as well as one of the regulators of other CYP enzymes [40], and our previous studies indicated a positive correlation between the activities of CYP2C11 and CYP3A on the one hand, and the serum GH concentration on the other in

1/2
Pharmaceutics 2021, 13, x 11 of 18 Table 1. Summary of the effects of the 5-day and 3-week treatment with CP-101,606 on the expres-sion and activity of liver cytochrome P450 enzymes.
The detailed analysis of the influence of glutamate receptor agonists and antagonists on GH release has shown that glutamate can elicit prominent and dual regulatory re-sponses on GH secretion, involving a predominantly stimulatory effect via ionotropic re-ceptors, as well as a minor inhibitory effect via metabotropic receptors [28]. Thus, the ac-tivation of NMDA receptors resulted in the stimulation of GH secretion; however, the stimulus did not originate in the pituitary, but was generated at the level of GHRH and/or somatostatin neurons. In accordance with the abovementioned neuroendocrine pathway, a decrease in the GHRH level and GH-related expression (mRNA and protein) and activ-ity of CYP2C11 in male rat liver was observed after a 5-day treatment with the selective NMDA receptor GluN2B subunit antagonist CP-101,606 in our experiment. GH is the main regulator of CYP2C11, as well as one of the regulators of other CYP enzymes [40], and our previous studies indicated a positive correlation between the activities of CYP2C11 and CYP3A on the one hand, and the serum GH concentration on the other in

3A1/2
Pharmaceutics 2021, 13, x   Table 1. Summary of the effects of the 5-day and 3-week treatment with CP-101 sion and activity of liver cytochrome P450 enzymes.
The detailed analysis of the influence of glutamate receptor agonists on GH release has shown that glutamate can elicit prominent and du sponses on GH secretion, involving a predominantly stimulatory effect v ceptors, as well as a minor inhibitory effect via metabotropic receptors [ tivation of NMDA receptors resulted in the stimulation of GH secretio stimulus did not originate in the pituitary, but was generated at the level somatostatin neurons. In accordance with the abovementioned neuroend a decrease in the GHRH level and GH-related expression (mRNA and p ity of CYP2C11 in male rat liver was observed after a 5-day treatment w NMDA receptor GluN2B subunit antagonist CP-101,606 in our experi main regulator of CYP2C11, as well as one of the regulators of other CY and our previous studies indicated a positive correlation between CYP2C11 and CYP3A on the one hand, and the serum GH concentratio
The detailed analysis of the influence of glutamate receptor agonists and antagonists on GH release has shown that glutamate can elicit prominent and dual regulatory responses on GH secretion, involving a predominantly stimulatory effect via ionotropic receptors, as well as a minor inhibitory effect via metabotropic receptors [28]. Thus, the activation of NMDA receptors resulted in the stimulation of GH secretion; however, the stimulus did not originate in the pituitary, but was generated at the level of GHRH and/or somatostatin neurons. In accordance with the abovementioned neuroendocrine pathway, a decrease in the GHRH level and GH-related expression (mRNA and protein) and activity of CYP2C11 in male rat liver was observed after a 5-day treatment with the selective NMDA receptor GluN2B subunit antagonist CP-101,606 in our experiment. GH is the main regulator of CYP2C11, as well as one of the regulators of other CYP enzymes [40], and our previous studies indicated a positive correlation between the activities of CYP2C11 and CYP3A on the one hand, and the serum GH concentration on the other in male rats [6]. Alternatively, an interplay of the glutamatergic system with other neuroendocrine regulators of GH release, such as the monoamine neurotransmitters dopamine, noradrenaline or serotonin seems also possible. NMDA receptors were shown to be present on catecholaminergic and indoleaminergic neurons and to affect the function of the monoaminergic systems in the brain [47,48]. An important role of the mentioned monoaminergic systems in the GH regulation has been documented [4,5,13,49]. On the other hand, the expression of CYP2C6 enzyme, which is less susceptible to neuroendocrine regulation, was not affected by a 5-day treatment with the investigated compound.  A decrease in the activity of CYP1A, 2A, 2B, 2C11 and 3A, but not in CYP2C6 was observed. The investigated CYP isoforms are regulated by hormones, such as growth hor-mone (GH), glucocorticoids (corticosterone) and thyroid hormones (triiodothyronine T3 and thyroxine T4) and via activation of the respective membrane, cytoplasmic or nuclear receptors, in this way regulating the transcription of CYP genes [40][41][42][43][44][45][46].
The detailed analysis of the influence of glutamate receptor agonists and antagonists on GH release has shown that glutamate can elicit prominent and dual regulatory re-sponses on GH secretion, involving a predominantly stimulatory effect via ionotropic re-ceptors, as well as a minor inhibitory effect via metabotropic receptors [28]. Thus, the ac-tivation of NMDA receptors resulted in the stimulation of GH secretion; however, the stimulus did not originate in the pituitary, but was generated at the level of GHRH and/or somatostatin neurons. In accordance with the abovementioned neuroendocrine pathway, a decrease in the GHRH level and GH-related expression (mRNA and protein) and activ-ity of CYP2C11 in male rat liver was observed after a 5-day treatment with the selective   A decrease in the activity of CYP1A, 2A, 2B, 2C11 and 3A, but not in CYP2C6 was observed. The investigated CYP isoforms are regulated by hormones, such as growth hor-mone (GH), glucocorticoids (corticosterone) and thyroid hormones (triiodothyronine T3 and thyroxine T4) and via activation of the respective membrane, cytoplasmic or nuclear receptors, in this way regulating the transcription of CYP genes [40][41][42][43][44][45][46].
The detailed analysis of the influence of glutamate receptor agonists and antagonists on GH release has shown that glutamate can elicit prominent and dual regulatory re-sponses on GH secretion, involving a predominantly stimulatory effect via ionotropic re-ceptors, as well as a minor inhibitory effect via metabotropic receptors [28]. Thus, the ac-tivation of NMDA receptors resulted in the stimulation of GH secretion; however, the stimulus did not originate in the pituitary, but was generated at the level of GHRH and/or somatostatin neurons. In accordance with the abovementioned neuroendocrine pathway, a decrease in the GHRH level and GH-related expression (mRNA and protein) and activ-ity of CYP2C11 in male rat liver was observed after a 5-day treatment with the selective A decrease in the activity of CYP1A, 2A, 2B, 2C11 and 3A, but not in C observed. The investigated CYP isoforms are regulated by hormones, such as mone (GH), glucocorticoids (corticosterone) and thyroid hormones (triiodo and thyroxine T4) and via activation of the respective membrane, cytoplasm receptors, in this way regulating the transcription of CYP genes [40][41][42][43][44][45][46].
The detailed analysis of the influence of glutamate receptor agonists and on GH release has shown that glutamate can elicit prominent and dual re sponses on GH secretion, involving a predominantly stimulatory effect via io ceptors, as well as a minor inhibitory effect via metabotropic receptors [28]. T tivation of NMDA receptors resulted in the stimulation of GH secretion; h stimulus did not originate in the pituitary, but was generated at the level of G somatostatin neurons. In accordance with the abovementioned neuroendocri a decrease in the GHRH level and GH-related expression (mRNA and protei ity of CYP2C11 in male rat liver was observed after a 5-day treatment with

3A1/2
Pharmaceutics 2021, 13, x   Table 1. Summary of the effects of the 5-day and 3-week trea sion and activity of liver cytochrome P450 enzymes.
↑, ↓ increase or decrease, respectively; − no change; n.t. not te A decrease in the activity of CYP1A, 2A, 2B, 2C11 observed. The investigated CYP isoforms are regulated mone (GH), glucocorticoids (corticosterone) and thyro and thyroxine T4) and via activation of the respective m receptors, in this way regulating the transcription of CY The detailed analysis of the influence of glutamate on GH release has shown that glutamate can elicit p sponses on GH secretion, involving a predominantly st ceptors, as well as a minor inhibitory effect via metabo tivation of NMDA receptors resulted in the stimulatio stimulus did not originate in the pituitary, but was gene somatostatin neurons. In accordance with the aboveme a decrease in the GHRH level and GH-related expressio ity of CYP2C11 in male rat liver was observed after a 5 A decrease in the activity of CYP1A, 2 observed. The investigated CYP isoforms are mone (GH), glucocorticoids (corticosterone) and thyroxine T4) and via activation of the r receptors, in this way regulating the transcri The detailed analysis of the influence of on GH release has shown that glutamate c sponses on GH secretion, involving a predo ceptors, as well as a minor inhibitory effect v tivation of NMDA receptors resulted in th stimulus did not originate in the pituitary, bu somatostatin neurons. In accordance with th a decrease in the GHRH level and GH-relate ity of CYP2C11 in male rat liver was observ  A decrease in the activity of CYP1A, 2A, 2B, 2C11 and 3 observed. The investigated CYP isoforms are regulated by horm mone (GH), glucocorticoids (corticosterone) and thyroid horm and thyroxine T4) and via activation of the respective membra receptors, in this way regulating the transcription of CYP gene

CYPs
The detailed analysis of the influence of glutamate recepto on GH release has shown that glutamate can elicit prominen sponses on GH secretion, involving a predominantly stimulato ceptors, as well as a minor inhibitory effect via metabotropic r tivation of NMDA receptors resulted in the stimulation of G stimulus did not originate in the pituitary, but was generated a somatostatin neurons. In accordance with the abovementioned a decrease in the GHRH level and GH-related expression (mRN ity of CYP2C11 in male rat liver was observed after a 5-day tr NMDA receptor GluN2B subunit antagonist CP-101,606 in o main regulator of CYP2C11, as well as one of the regulators o and our previous studies indicated a positive correlation CYP2C11 and CYP3A on the one hand, and the serum GH co male rats [6]. Alternatively, an interplay of the glutamatergic s docrine regulators of GH release, such as the monoamine ne noradrenaline or serotonin seems also possible. NMDA recep sent on catecholaminergic and indoleaminergic neurons and t monoaminergic systems in the brain [47,48]. An important ro aminergic systems in the GH regulation has been documente hand, the expression of CYP2C6 enzyme, which is less suscept ulation, was not affected by a 5-day treatment with the investi  A decrease in the activity of CYP1A, 2A, 2 observed. The investigated CYP isoforms are reg mone (GH), glucocorticoids (corticosterone) an and thyroxine T4) and via activation of the resp receptors, in this way regulating the transcriptio The detailed analysis of the influence of glu on GH release has shown that glutamate can sponses on GH secretion, involving a predomin ceptors, as well as a minor inhibitory effect via tivation of NMDA receptors resulted in the st stimulus did not originate in the pituitary, but w somatostatin neurons. In accordance with the ab a decrease in the GHRH level and GH-related e ity of CYP2C11 in male rat liver was observed NMDA receptor GluN2B subunit antagonist C main regulator of CYP2C11, as well as one of th and our previous studies indicated a positiv CYP2C11 and CYP3A on the one hand, and the male rats [6]. Alternatively, an interplay of the g docrine regulators of GH release, such as the m noradrenaline or serotonin seems also possible. sent on catecholaminergic and indoleaminergic monoaminergic systems in the brain [47,48]. An aminergic systems in the GH regulation has be hand, the expression of CYP2C6 enzyme, which ulation, was not affected by a 5-day treatment w  A decrease in the activity of observed. The investigated CYP is mone (GH), glucocorticoids (corti and thyroxine T4) and via activati receptors, in this way regulating t The detailed analysis of the in on GH release has shown that g sponses on GH secretion, involvin ceptors, as well as a minor inhibit tivation of NMDA receptors resu stimulus did not originate in the p somatostatin neurons. In accordan a decrease in the GHRH level and ity of CYP2C11 in male rat liver w NMDA receptor GluN2B subuni main regulator of CYP2C11, as w and our previous studies indica CYP2C11 and CYP3A on the one male rats [6]. Alternatively, an int docrine regulators of GH release, noradrenaline or serotonin seems sent on catecholaminergic and ind monoaminergic systems in the br aminergic systems in the GH reg hand, the expression of CYP2C6 e ulation, was not affected by a 5-da A decrease in the activity of CYP1A, 2A, 2B, 2C11 and 3A, but not in CYP2C6 was observed. The investigated CYP isoforms are regulated by hormones, such as growth hormone (GH), glucocorticoids (corticosterone) and thyroid hormones (triiodothyronine T 3 and thyroxine T 4 ) and via activation of the respective membrane, cytoplasmic or nuclear receptors, in this way regulating the transcription of CYP genes [40][41][42][43][44][45][46].
The detailed analysis of the influence of glutamate receptor agonists and antagonists on GH release has shown that glutamate can elicit prominent and dual regulatory responses on GH secretion, involving a predominantly stimulatory effect via ionotropic receptors, as well as a minor inhibitory effect via metabotropic receptors [28]. Thus, the activation of NMDA receptors resulted in the stimulation of GH secretion; however, the stimulus did not originate in the pituitary, but was generated at the level of GHRH and/or somatostatin neurons. In accordance with the abovementioned neuroendocrine pathway, a decrease in the GHRH level and GH-related expression (mRNA and protein) and activity of CYP2C11 in male rat liver was observed after a 5-day treatment with the selective NMDA receptor GluN2B subunit antagonist CP-101,606 in our experiment. GH is the main regulator of CYP2C11, as well as one of the regulators of other CYP enzymes [40], and our previous studies indicated a positive correlation between the activities of CYP2C11 and CYP3A on the one hand, and the serum GH concentration on the other in male rats [6]. Alternatively, an interplay of the glutamatergic system with other neuroendocrine regulators of GH release, such as the monoamine neurotransmitters dopamine, noradrenaline or serotonin seems also possible. NMDA receptors were shown to be present on catecholaminergic and indoleaminergic neurons and to affect the function of the monoaminergic systems in the brain [47,48]. An important role of the mentioned monoaminergic systems in the GH regulation has been documented [4,5,13,49]. On the other hand, the expression of CYP2C6 enzyme, which is less susceptible to neuroendocrine regulation, was not affected by a 5-day treatment with the investigated compound.
There is also strong evidence that glutamate drives the hypothalamo-pituitary-adrenal (HPA) axis stress responses through postsynaptic ionotropic glutamate receptors (NMDA and non-NMDA) localized on neurons in the hypothalamic paraventricular nuclei [27]. Accordingly, a decrease in the serum concentration of corticosterone and corticosteronerelated expression and activity of liver CYP3A was observed after a 5-day treatment with the selective NMDA receptor GluN2B subunit antagonist in our experiment. The hypothetical mechanism of the observed changes in CYP enzyme activities after subchronic treatment with CP-101,606 is presented in Figure 9. There is also strong evidence that glutamate drives the hypothalamo-pituitary-adrenal (HPA) axis stress responses through postsynaptic ionotropic glutamate receptors (NMDA and non-NMDA) localized on neurons in the hypothalamic paraventricular nuclei [27]. Accordingly, a decrease in the serum concentration of corticosterone and corticosterone-related expression and activity of liver CYP3A was observed after a 5-day treatment with the selective NMDA receptor GluN2B subunit antagonist in our experiment. The hypothetical mechanism of the observed changes in CYP enzyme activities after subchronic treatment with CP-101,606 is presented in Figure 9. Figure 9. A hypothetical mechanism of neuroendocrine regulation of liver cytochrome P450 by the selective NMDA receptor GluN2B subunit antagonist CP-101,606. Through its antagonistic effect on NMDA receptors (NMDARs) in the paraventricular (PVN) and arcuate (ARC) nuclei of the hypothalamus, CP-101,606 negatively regulates growth hormone (GH) and corticosterone secretion and, in turn, the cytochrome P450 expression in the liver. CRH, corticotropin-releasing hormone; TRH, thyrotropin-releasing hormone; GHRH, growth hormone-releasing hormone; ACTH, adrenocorticotropic hormone.
In the case of other investigated cytochrome P450 enzymes, a correlation between the activity, protein and mRNA level was less pronounced, which may suggest involvement of other mechanisms, such as posttranscriptional regulation of CYP1A (an increase in CYP1A1/2 mRNA, but a decrease in the CYP1A protein and activity) or posttranslational modification of CYP2A and CYP2B protein (an increase in enzyme activity at no change in the enzyme protein and mRNA) after a 5-day treatment with CP-101,606.
After a 3-week administration of the selective NMDA receptor GluN2B subunit antagonist CP-101,606 less changes in the investigated enzymes were found, probably as a result of adaptive mechanisms. Thus, the decreased serum concentration of GH, observed after a 5-day treatment, returned to the control value, while that of corticosterone was still slightly diminished. A decrease in the CYP3A1 enzyme activity and protein level, observed after a 5-day treatment, was maintained at a similar level after a 3-week treatment; Figure 9. A hypothetical mechanism of neuroendocrine regulation of liver cytochrome P450 by the selective NMDA receptor GluN2B subunit antagonist CP-101,606. Through its antagonistic effect on NMDA receptors (NMDARs) in the paraventricular (PVN) and arcuate (ARC) nuclei of the hypothalamus, CP-101,606 negatively regulates growth hormone (GH) and corticosterone secretion and, in turn, the cytochrome P450 expression in the liver. CRH, corticotropin-releasing hormone; TRH, thyrotropin-releasing hormone; GHRH, growth hormone-releasing hormone; ACTH, adrenocorticotropic hormone.
In the case of other investigated cytochrome P450 enzymes, a correlation between the activity, protein and mRNA level was less pronounced, which may suggest involvement of other mechanisms, such as posttranscriptional regulation of CYP1A (an increase in CYP1A1/2 mRNA, but a decrease in the CYP1A protein and activity) or posttranslational modification of CYP2A and CYP2B protein (an increase in enzyme activity at no change in the enzyme protein and mRNA) after a 5-day treatment with CP-101,606.
After a 3-week administration of the selective NMDA receptor GluN2B subunit antagonist CP-101,606 less changes in the investigated enzymes were found, probably as a result of adaptive mechanisms. Thus, the decreased serum concentration of GH, observed after a 5-day treatment, returned to the control value, while that of corticosterone was still slightly diminished. A decrease in the CYP3A1 enzyme activity and protein level, observed after a 5-day treatment, was maintained at a similar level after a 3-week treatment; however, no change in the mRNA level was observed, which suggest a posttranscriptional mechanism of the enzyme regulation after prolonged treatment with CP-101,606. Interestingly, the CYP1A activity increased (at no change in the enzyme protein and mRNA), which is contrary to the result observed after 5-day treatment. This may also be caused by some adaptive changes in the functioning of CYP1A protein that developed during prolonged administration of CP-101,606. Neuroimmune mechanisms do not seem to be involved in the effects produced by CP-101,606 on CYP enzymes, since the level of proinflammatory cytokine IL-6, which negatively regulates the expression of cytochrome P450 [50] has not been changed.
The results obtained for the selective NMDA receptor GluN2B subunit antagonist CP-101,606 in our experiment differ from those of Loch et al. and Chan et al. [51,52] for the non-subunit-selective NMDA receptor antagonist ketamine. When administered in vivo to rats in a single dose of 10 mg/kg ip., ketamine only weakly decreased CYP2D and CYP3A activity [51], but when given at doses of 10-80 mg/kg ip. twice daily for 4 days, it induced CYP enzymes (CYP1A, 2B, 2E1 and 3A) after the highest dosage [52], which exceeded by far that applied in animal pharmacological tests to show antidepressant action [53]. The reason for this discrepancy may be related to different molecular mechanism of action within NMDA receptor (receptor subunit selectivity), the applied dosages and chemical structures of the two drugs, which may affect drug action on cytochrome P450 at the level of the neuroendocrine system and liver. It seems also worth mentioning that the distribution of particular mGluN2 subunits of NMDA receptor within the brain is different, which makes the action of CP-101,606 also brain region-dependent [35]. On the other hand, ketamine is metabolized to norketamine and hydroxynorketamine. The latter metabolite (2R,6R-HNK) acts at AMPA receptors and metabotropic mGlu 2 receptors, broadening in this way the spectrum of ketamine action at glutamatergic receptors [54,55].
In conclusion, the obtained results imply the contribution of brain NMDA glutamate receptors to the neuroendocrine regulation of cytochrome P450 expression. However, further studies after intracerebral administration of CP-101,606 are necessary to confirm the central neuroendocrine regulation of cytochrome P450 by the applied selective antagonist of GluN2B subunit of NMDA receptor. It seems that there is a potential for metabolic drug-drug interactions with drugs acting on NMDA receptors.

Animals and Materials
All procedures involving animals and their care were conducted in conformity with the NIH Guide for the Care and Use of Laboratory Animals and the Ethics Committee of the Maj Institute of Pharmacology, Polish Academy of Sciences, Krakow. Adult male Wistar Han rats weighing 225-250 g were purchased from Charles River Laboratories (Sulzfeld, Germany). All animals were housed under controlled conditions with an artificial 12-h light/dark cycle (lights on from 07:00 to 19:00), 55 ± 5% humidity, and a temperature of 22 ± 2 • C. Food and tap water were freely available. To avoid any influence of the digestive process on the activity of CYP enzymes, eighteen hours before experiment, food was taken away from rats.

Determination of Hormone and Cytokine Levels
Hormonal responses were measured 2 h after the repeated administration of CP-101,606. The levels of hormones in serum or pituitary were measured using ELISA kits for GHRH, GH, corticosterone and thyroid hormones (T 3 , T 4 ). The serum concentrations of cytokine were analyzed using the IL-6 ELISA kits. Absorbance was measured using a Synergy Mx Monochromator-Based Multi-Mode Microplate Reader (Biotek, Winooski, VT, USA).
The hormone and cytokine concentrations were calculated from 8-10 rats for the control and drug-treated group in the 5-day experiment or from 11-13 animals for the control and CP-101,606-treated group in the 3-week study.

RNA Isolation and Quantitative Real-Time Polymerase Chain Reaction (qRT-PCR)
The RT-qPCR method used in this study has been previously described in detail by Rysz et al. [9]. Briefly, RNA was extracted from individual liver samples using a mirVana isolation kit. RNA was reverse-transcribed using a Transcriptor High-Fidelity cDNA synthesis kit. Quantitative real-time PCR was performed in duplicate with TaqMan Gene Expression Assays using TaqMan Expression Master Mix, species-specific TaqMan type probes and primers ( Table 2) and Bio-Rad CFX96 PCR system (Bio-Rad, Hercules, CA, USA). Real-time PCR was conducted under the standard conditions (50 • C for 2 min and 95 • C for 10 min followed by 40 cycles of 95 • C for 15 s and 60 • C for 1 min). The abundance of RNA was achieved by a comparative delta-delta Ct method (2 −∆∆Ct ). The expression of the two reference genes: β-actin (ACTB) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was also measured. The obtained results concerning CYP mRNAs were normalized to the ACTB expression (ACTB expression was stable compared to that of GAPDH after CP-101,606 treatment). Table 2. List of TaqMan ® Gene Expression Assays used in the study.

Gene Name
Assay ID The results of the CYP mRNA levels were calculated from 8-10 rats for the control and CP-101,606-treated group in the 5-day experiment or from 11-13 animals for the control and CP-101,606-treated group in the 3-week study.

Statistical Analysis
The obtained results are reported as the mean ± S.E.M. of 8-10 rats for the control and CP-101,606-treated group in the 5-day experiment or of 11-13 rats for the control and CP-101,606-treated group in the 3-week study, except for the western immunoblot analysis, where all the results were obtained from 8 animals for each group and experiment. Changes in the concentrations of hormones and interleukin, as well as the liver CYP enzyme activities, protein and mRNA levels, were statistically assessed using a two-tailed Student's t-test. The changes found were considered as statistically significant when p < 0.05.

Conclusions
The presented results show a new possible physiological regulatory mechanism of liver cytochrome P450 involving the glutamatergic system. The obtained results imply the contribution of NMDA glutamate receptors to the neuroendocrine regulation of cytochrome P450 expression. They suggest that, apart from their targeted therapeutic effect as psychotropic drugs, new drugs acting via NMDA receptors may affect neuroendocrine regulation of physiological processes including the expression of cytochrome P450, in particular, during the first weeks of therapy. Thus different drug-drug interactions could occur in relation to the regulation of cytochrome P450 expression/activity via NMDA receptors during therapy with drugs acting on these receptors.