Search Results (46)

Background: Adolescence is a sensitive period for brain maturation during which exposure to Δ⁹-tetrahydrocannabinol (THC) can induce long-lasting neurobehavioral alterations. Yet, preclinical and clinical studies report inconsistent long-term outcomes of adolescent THC exposure, ranging from clear impairments to apparently normalizing effects. We hypothesize that these discrepancies reflect stable individual differences in stress-coping abilities. Methods: To test this, selectively bred Dominant (Dom; stress-resilient, risk-prone) and Submissive (Sub; stress-vulnerable, depressive-like) Sabra mice received THC or vehicle during adolescence and were assessed in adulthood. Results: Anxiety-like and exploratory behavior, measured in the hole-board test, were differentially affected by THC as a function of stress vulnerability: in Sub mice, THC increased exploration and reduced anxiety-like behavior, whereas in Dom mice THC produced the opposite pattern. Recognition memory, evaluated by the novel object recognition test, showed modest, line-dependent alterations. Sensitivity to N-methyl-D-aspartate (NMDA) receptor hypofunction, a widely used index of vulnerability to schizophrenia-like symptoms, was examined using MK-801-induced locomotion. Adolescent THC potentiated MK-801-evoked hyperlocomotion in Dom mice but attenuated it in Sub mice. Conclusions: In the context of increasing medical and recreational cannabis exposure, these in vivo findings suggest that stress-vulnerability-related traits may be an important variable to consider in future preclinical and translational studies of adolescent THC exposure. Full article

Cardiotonic steroids (CTS) can modulate central nervous system function through their interaction with the Na⁺,K⁺-ATPase, affecting dopaminergic transmission. While the CTS ouabain is known to induce mania-like behavior and oxidative damage, the effects of other CTS are less clear. This study examined the effects of 14-day intracerebroventricular administration of 1.5 μL 100 μM marinobufagenin (MBG) on locomotion, gait, monoamine metabolism, and oxidative stress markers (MDA, SOD, catalase, MAO-B) in C57BL/6 mice. Chronic MBG caused increased locomotor activity and time spent in the center of the open field. Unlike ouabain, chronic MBG did not impair motor function, evaluated via gait analysis. MBG elevated striatal MAO-B activity and reduced prefrontal MDA levels, with no changes in SOD or catalase, indicating that it did not cause oxidative stress. However, it did affect dopamine and serotonin metabolism. Monoamine tissue content evaluation on day 15 showed increased dopamine turnover in the striatum and brain stem, and a decrease in the thalamus. Norepinephrine levels increased in the striatum and hippocampus. Serotonin turnover increased in the prefrontal cortex. These results indicate that chronic MBG increases locomotion and reduces anxiety-like behavior through region-specific modulation of dopaminergic and serotonergic signaling distinct from that caused by ouabain. Full article

Background: Schizophrenia is a chronic neuropsychiatric disorder characterized by cognitive impairment, behavioral abnormalities, neuroinflammation, and oxidative stress. Increasing evidence suggests that dysregulated inflammatory cytokines and impaired antioxidant defenses contribute to schizophrenia pathophysiology. This study investigated the neuroprotective and anti-inflammatory effects of Gallic Acid (GA) in a ketamine-induced experimental schizophrenia model. Methods: Thirty male Balb/C mice were randomly divided into control, ketamine, and ketamine + GA groups. Schizophrenia was induced with ketamine (25 mg/kg/day) for 7 days, while the treatment group additionally received GA (60 mg/kg/day) for another 7 days. Behavioral tests, including open field, novel object recognition, and tail suspension tests, were performed to evaluate locomotor activity, cognition, and depressive-like behavior. Tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), interleukin-18 (IL-18), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), total antioxidant status (TAS), and total oxidant status (TOS) levels were analyzed in hippocampal and prefrontal cortex tissues to assess inflammatory and oxidative stress-related alterations. Results: Ketamine induced schizophrenia-like behaviors, including hyperlocomotion, memory impairment, and increased immobility. These behavioral alterations were accompanied by significantly elevated TNF-α, IL-1β, IL-18, and TOS levels, alongside reduced SOD, CAT, GSH-Px, and TAS levels in the hippocampus and prefrontal cortex. GA treatment ameliorated behavioral impairments, restored antioxidant enzymes, increased TAS levels, and reduced pro-inflammatory cytokines and TOS in these brain regions. Conclusions: GA exerted neuroprotective effects in the ketamine-induced schizophrenia model by reducing oxidative stress, neuroinflammation, and behavioral deficits. These findings suggest that Gallic Acid may serve as a promising therapeutic candidate for schizophrenia through modulation of inflammatory and oxidative stress pathways. Full article

Our goal in this study was to determine whether functional variation in the human RGS12 gene influences behavioral responses to psychostimulants such as methylphenidate, thereby informing whether such genetic findings should affect the clinical use of this central nervous system (CNS)-stimulating agent in bipolar disorder (BD) patients with comorbid attention-deficit/hyperactivity disorder (ADHD). The use of psychostimulants for ADHD in BD remains controversial due to concerns about mood destabilization, although recent systematic reviews indicate that methylphenidates and amphetamines can be safe and effective when used with mood stabilizers. RGS12, a striatally enriched regulator of κ-opioid receptor signaling and dopamine transporter (DAT) function, has been implicated in altered dopaminergic responses to psychostimulants. A recently characterized R59Q reduction-of-function mutation within RGS12 has been associated with familial bipolar disorder, further highlighting its potential relevance to mood and psychostimulant responsiveness. Rgs12-deficient mice were evaluated for behavioral responses to methylphenidate (i.e., locomotor hyperactivity) and compared with responses to dopamine transporter-dependent stimulants. Rgs12 deficiency was seen to reduce hyperlocomotion with amphetamine, and with methamphetamine but not with methylphenidate, which was instead observed to elicit normal hyperlocomotor responses across all doses. Methylphenidate responsiveness remains intact despite the loss of RGS12 function, suggesting that RGS12 functional variation in the human condition should not contraindicate methylphenidate use in mood-stabilized BD/ADHD comorbidity. Full article

Background/Objectives: Lithium remains the first choice for long-term prophylaxis of mood episodes in bipolar disorder (BD), but only 30% of patients will respond, and there is no reliable method by which to predict treatment response. Ketamine is a rapid antidepressant therapy which ostensibly yields greater results in patients with clinical phenotypes that are classically associated with lithium non-response. This inspired a scoping review to map the overlapping and divergent clinical and mechanistic evidence for acute ketamine response and long-term prophylactic lithium therapy in BD. Methods: We conducted a scoping review of clinical and preclinical studies that examine convergent and divergent predictors and mechanisms of acute response to ketamine and long-term response to lithium. Results: Data from 19 preclinical studies show mechanistic convergence of ketamine and lithium on the GSK-3β/mTOR pathways, and enhancement of synaptic plasticity. Furthermore, lithium appears to consistently limit ketamine-related oxidative stress and hyperlocomotion. However, data from the 23 clinical studies suggest divergence of predictors of response to ketamine and lithium in BD, with ketamine response associated with metabolic risk factors, anxiety/mixed features, and non-melancholic presentations, which are generally predictors of poorer prophylactic lithium response. No study directly tested ketamine response as a predictor of prophylactic lithium response. An important limitation is that clinical studies of ketamine are enriched for lithium-refractory populations and have often included mixed unipolar and bipolar cases. Conclusions: Overall, existing data support mechanistic overlap but clinical divergence between ketamine and lithium responders, though this is confounded by sampling bias. We must therefore undertake longitudinal studies of prophylactic lithium therapy among patients with BD who received ketamine for acute antidepressant treatment in order to investigate if responsiveness to ketamine predicts response to lithium, and establish control over BD earlier in the course of illness. Full article

The pituitary adenylate cyclase-activating polypeptide receptor 1 (PAC1) plays a pivotal role in central nervous system development and homeostasis. Comparisons of PAC1 knockout (PAC1^−/−), heterozygous (PAC1^+/−) and wild-type (PAC1^+/+) mice demonstrate that PAC1 deficiency severely impairs pre-weaning survival and results in marked developmental deficits, including reduced postnatal weight and altered locomotor behavior. PAC1^−/− mice exhibited hyperlocomotion, reduced anxiety-like behavior, and transient deficits in motor coordination. Gene expression analyses revealed widespread dysregulation of oligodendrocyte-associated markers, with significant myelin reduction and decreased mature oligodendrocyte density in the corpus callosum. ER stress was evidenced in both white matter and motor cortex, as indicated by altered expression of UPR-related genes and increased phosphorylated (p)IRE1⁺ neurons. Retinal morphology was compromised in PAC1^−/− animals, with reduced overall retinal and ganglion cell layer thickness. Notably, no gross morphological or molecular abnormalities were detected in the spinal cord regarding myelin content or MBP expression; however, synaptic marker expression was selectively reduced in the ventral horn of PAC1-deficient mice. Together, these findings highlight a critical role for PAC1 in oligodendrocyte maturation, retinal development, and synaptogenesis, providing new insights with relevance in multiple sclerosis and other neurodevelopmental and neurodegenerative conditions. Full article

Neuropeptide FF (NPFF) receptor antagonists prevent morphine-mediated antinociceptive tolerance, and compounds with dual mu opioid receptor (MOR) agonist and NPFF antagonist activity produce antinociception without tolerance. Compounds synthesized showed affinities in radioligand competition binding assays in the nM and µM range at the opioid and NPFF receptors, respectively, and displayed substitution-dependent functional profiles in the [³⁵S]GTPγS functional assay. From six compounds screened in vivo for antinociception and ability to prevent NPFF-induced hyperalgesia in mouse warm water tail withdrawal tests, compound 22b produced dose-dependent MOR-mediated antinociception with an ED₅₀ value (and 95% confidence interval) of 6.88 (4.71–9.47) nmol, i.c.v., and also prevented NPFF-induced hyperalgesia. Meanwhile, 22b did not demonstrate the respiratory depression, hyperlocomotion, or impaired intestinal transit of morphine. Moreover, repeated treatment with 22b produced a 1.6-fold rightward shift in antinociceptive dose response, significantly less acute antinociceptive tolerance than morphine. Evaluated for microsomal stability in vitro and in vivo pharmacokinetic profile, 22b showed suitable microsomal stability paired in vivo with a large apparent volume of distribution and a clearance smaller than the hepatic flow in rats, suggesting no extra-hepatic metabolism. In conclusion, the present study confirms that dual-action opioid–NPFF ligands may offer therapeutic promise as analgesics with fewer liabilities of use. Full article

Sleep deprivation (SD) induces significant neurobiological changes, including oxidative stress, neuroinflammation, and behavioural impairments. This study was designed as a proof of concept to assess the potential for modulating the effects of SD through a short-term seven-day administration of Cornus mas (C. mas) in a rapid eye movement (REM) SD rodent paradigm. Adult male Wistar rats were randomised in four groups (n = 7): control, C. mas (CM), sleep deprivation (SD), and sleep deprivation with C. mas (SD + CM). Behaviourally, SD induced hyperactivity and hyperlocomotion. SD determined histological alterations in the prefrontal cortex and corpus callosum myelin coupled with ultrastructural mitochondrial and cellular abnormalities in the prefrontal cortex, hippocampus, and pineal gland. Despite evidence of systemic oxidative stress coupled with decreased serum GABA and BDNF following SD, no significant changes were observed in redox markers or inflammatory cytokine levels (TNF-α, IL-1β) within the prefrontal cortex or hippocampus. C. mas extract has shown an overall modest modulatory action, mainly evidenced on behavioural, histological, and ultrastructural parameters. Taken together, these findings highlight behavioural changes and region-specific molecular and structural abnormalities following prolonged REM SD in rats. Full article

Background/Objectives: Cognitive deficits and negative symptoms associated with schizophrenia are poorly managed by current antipsychotics. In order to develop effective treatments, refining animal models of neurodevelopmental disorders is essential. Methods: To address their multifactorial etiology, we developed a new three-hit mouse model based on the hypoglutamatergic hypothesis of the pathology combined with early stress, offering strong construct validity. Thus, a genetic susceptibility (serine racemase deletion) was associated with an early environmental stress (24 h maternal separation at 9 days of age) and a further pharmacological treatment with phencyclidine (PCP, a glutamate receptor antagonist treatment, 10 mg/kg/day, from 8 to 10 weeks of age). The face validity of this model was assessed in female mice 1 and 6 weeks after the end of PCP treatment by a set of behavioral experiments investigating positive- and negative-like symptoms and cognitive deficits. Results: Our results showed that the three-hit mice displayed persistent hyperlocomotion (positive-like symptoms) and social behavior impairment deficits (negative-like symptoms) but non-persistent spatial working memory deficits (cognitive symptoms). Conclusions: Our work confirms the usefulness of a three-hit combination to model, particularly for negative-like symptoms associated with schizophrenia and other psychiatric disorders. The model therefore gathers powerful construct and face validities and supports an involvement of glutamate dysfunction in behavioral symptoms. Full article

Social withdrawal in rodents is a measure of asociality, an important negative symptom of schizophrenia. The Roman high- (RHA) and low-avoidance (RLA) rat strains have been reported to exhibit differential profiles in schizophrenia-relevant behavioral phenotypes. This investigation was focused on the study of social and non-social behavior of these two rat strains following acute administration of dizocilpine (MK801, an NMDA receptor antagonist), a pharmacological model of schizophrenia-like features used to produce asociality and hyperactivity. Also, since oxytocin (OXT) has been proposed as a natural antipsychotic and a potential adjunctive therapy for social deficits in schizophrenia, we have evaluated the effects of OXT administration and its ability to reverse the MK801-impairing effects on social and non-social behavior and MK801-induced hyperactivity. MK801 administration produced hyperlocomotion and a decrease in social and non-social behavior in both rat strains, but these drug effects were clearly more marked in RHA rats. OXT (0.04 mg/kg and 0.2 mg/kg) attenuated MK801-induced hyperlocomotion in both rat strains, although this effect was more marked in RHA rats. The MK801-decreasing effect on exploration of the “social hole” was moderately but significantly attenuated only in RLA rats. This study is the first to demonstrate the differential effects of OXT on MK801-induced impairments in the two Roman rat strains, providing some support for the potential therapeutic effects of OXT against schizophrenia-like symptoms, including both a positive-like symptom (i.e., MK801-induced hyperlocomotion) and a negative-like symptom (i.e., MK801 decrease in social behavior), while highlighting the importance of the genetic background (i.e., the rat strain) in influencing the effects of both MK801 and oxytocin. Full article

Background: Tourette syndrome is a neurodevelopmental movement disorder involving basal ganglia dysfunction. PDE10A inhibitors modulate signaling in the striatal basal ganglia nuclei and are thus of interest as potential therapeutics in treating Tourette syndrome and other movement disorders. Methods: The preclinical pharmacology and toxicology, human safety and tolerability, and human PET striatal enzyme occupancy data for the PDE10A inhibitor EM-221 are presented. Results: EM-221 inhibited PDE10A with an in vitro IC50 of 9 pM and was >100,000 selective vs. other PDEs and other CNS receptors and enzymes. In rats, at doses of 0.05–0.50 mg/kg, EM-221 reduced hyperlocomotion and the disruption of prepulse inhibition induced by MK-801, attenuated conditioned avoidance, and facilitated novel object recognition, consistent with PDE10A’s inhibition. EM-221 displayed no genotoxicity and was well tolerated up to 300 mg/kg in rats and 100 mg/kg in dogs. In single- and multiple-day ascending dose studies in healthy human volunteers, EM-221 was well tolerated up to 10 mg, with a maximum tolerated dose of 15 mg. PET imaging indicated that a PDE10A enzyme occupancy of up to 92.8% was achieved with a ~24 h half-life. Conclusions: The preclinical and clinical data presented here support the study of EM-221 in phase 2 trials of Tourette syndrome and other movement disorders. Full article

In orbital and ground-based experiments, it has been demonstrated that ionizing radiation (IR) can stimulate the locomotor and exploratory activity of rodents, but the underlying mechanism of this phenomenon remains undisclosed. Here, we studied the effect of combined IR (0.4 Gy γ-rays and 0.14 Gy carbon-12 nuclei) on the locomotor and exploratory activity of rats, and assessed the sensorimotor cortex volume by magnetic resonance imaging-based morphometry at 1 week and 7 months post-irradiation. The sensorimotor cortex tissues were processed to determine whether the behavioral and morphologic effects were associated with changes in neurotrophin content. The irradiated rats were characterized by increased locomotor and exploratory activity, as well as novelty-seeking behavior, at 3 days post-irradiation. At the same time, only unirradiated rats experienced a significant decrease in the sensorimotor cortex volume at 7 months. While there were no significant differences at 1 week, at 7 months, the irradiated rats were characterized by higher neurotrophin-3 and neurotrophin-4 content in the sensorimotor cortex. Thus, IR prevents the age-associated decrease in the sensorimotor cortex volume, which is associated with neurotrophic and neurogenic changes. Meanwhile, IR-induced increases in locomotor activity may be the cause of the observed changes. Full article

Chronic opioid treatments dysregulate the glutamatergic system, inducing a hyperglutamatergic state in mesocorticolimbic brain regions. This study investigated the effects of exposure to hydrocodone overdose on locomotor activity, expression of target proteins related to the glutamatergic system, signaling kinases, and neuroinflammatory factors in the nucleus accumbens. The locomotor activity of mice was measured using the Comprehensive Laboratory Animal Monitoring System (CLAMS). CLAMS data showed that exposure to hydrocodone overdose increased locomotion activity in mice. This study tested ceftriaxone, known to upregulate major glutamate transporter 1 (GLT-1), in mice exposed to an overdose of hydrocodone. Thus, ceftriaxone normalized hydrocodone-induced hyperlocomotion activity in mice. Furthermore, exposure to hydrocodone overdose downregulated GLT-1, cystine/glutamate antiporter (xCT), and extracellular signal-regulated kinase activity (p-ERK/ERK) expression in the nucleus accumbens. However, exposure to an overdose of hydrocodone increased metabotropic glutamate receptor 5 (mGluR5), neuronal nitric oxide synthase activity (p-nNOS/nNOS), and receptor for advanced glycation end products (RAGE) expression in the nucleus accumbens. Importantly, ceftriaxone treatment attenuated hydrocodone-induced upregulation of mGluR5, p-nNOS/nNOS, and RAGE, as well as hydrocodone-induced downregulation of GLT-1, xCT, and p-ERK/ERK expression. These data demonstrated that exposure to hydrocodone overdose can cause dysregulation of the glutamatergic system, neuroinflammation, hyperlocomotion activity, and the potential therapeutic role of ceftriaxone in attenuating these effects. Full article

Peptide-based opioid ligands are important candidates for the development of novel, safer, and more effective analgesics to treat pain. To develop peptide-based safer analgesics, we synthesized a mixture-based cyclic pentapeptide library containing a total of 24,624 pentapeptides and screened the mixture-based library samples using a 55 °C warm water tail-withdrawal assay. Using this phenotypic screening approach, we deconvoluted the mixture-based samples to identify a novel cyclic peptide Tyr-[D-Lys-Dap(Ant)-Thr-Gly] (CycloAnt), which produced dose- and time-dependent antinociception with an ED₅₀ (and 95% confidence interval) of 0.70 (0.52–0.97) mg/kg i.p. mediated by the mu-opioid receptor (MOR). Additionally, higher doses (≥3 mg/kg, i.p.) of CycloAnt antagonized delta-opioid receptors (DOR) for at least 3 h. Pharmacological characterization of CycloAnt showed the cyclic peptide did not reduce breathing rate in mice at doses up to 15 times the analgesic ED₅₀ value, and produced dramatically less hyperlocomotion than the MOR agonist, morphine. While chronic administration of CycloAnt resulted in antinociceptive tolerance, it was without opioid-induced hyperalgesia and with significantly reduced signs of naloxone-precipitated withdrawal, which suggested reduced physical dependence compared to morphine. Collectively, the results suggest this dual MOR/DOR multifunctional ligand is an excellent lead for the development of peptide-based safer analgesics. Full article

Febrile seizure (FS), which occurs as a response to fever, is the most common seizure that occurs in infants and young children. FS is usually accompanied by diverse neuropsychiatric symptoms, including impaired social behaviors; however, research on neuropsychiatric disorders and hippocampal inflammatory changes following febrile seizure occurrences is very limited. Here, we provide evidence linking FS occurrence with ASD pathogenesis in rats. We developed an FS juvenile rats model and found ASD-like abnormal behaviors including deficits in social novelty, repetitive behaviors, and hyperlocomotion. In addition, FS model juvenile rats showed enhanced levels of gliosis and inflammation in the hippocampal CA2 region and cerebellum. Furthermore, abnormal levels of social and repetitive behaviors persisted in adults FS model rats. These findings suggest that the inflammatory response triggered by febrile seizures in young children could potentially serve as a mediator of social cognitive impairments. Full article