Search Results (20)

Deregulation of striatal neurotransmission is a key pathogenetic mechanism in neurodevelopmental disorders such as attention deficit hyperactivity disorder (ADHD) and autism. In the present study, we applied a proteomic approach to demonstrate shifts in striatal protein expression in rats with heterozygous (DAT-Het) and homozygous (DAT-KO) dopamine transporter (DAT) gene knockouts. These animals model dose-dependent ADHD- and autism-like behaviors, ranging from slightly increased activity and social disturbances in DAT-Het rats to a pronounced phenotype in DAT-KO rats. We revealed pronounced changes in the proteomic profiles of both groups, associated primarily with deregulation of proteins involved in energy and carbon metabolism. Furthermore, we identified changes in vesicular transport proteins specific to DAT-KO and DAT-Het rats. Since these changes involved SNARE complex components, we evaluated SNARE mRNA expression in our models and public transcriptomic data for mouse models of neurodevelopmental disorders, including Mbd5 gene haploinsufficiency and a polygenic model of ADHD. No significant changes in mRNA levels were revealed in any model. Thus, the identified protein expression changes likely depend on post-transcriptional mechanisms. These data suggest a deregulation of metabolism in DAT-Het rats, which becomes more pronounced in DAT-KO rats. Full article

Background: The role of dopamine in brain functions has been well established, and dopamine imbalances can cause problems in working memory and spatial learning. The dopamine transporter (DAT) plays a significant role in dopamine regulation. Rats with a knockout of the dopamine transporter gene (DAT-KO), the model of attention deficit hyperactivity disorder (ADHD), are characterized by hyperdopaminergia and spatial memory impairments. Methods: Rats were trained to manipulate objects and recognize their spatial location and shape using RedBox apparatus. They needed to move a distant object to receive a food reward. After changing the shape and spatial location of objects, the ability to re-learning was evaluated. Results: We demonstrated that including objects to manipulate in the task conditions enables faster and stable learning of DAT-KO rats. The shape of the object did not influence the level of task performance, but changing the spatial location of the object led to the impairment of task performance in hyperactive rats. Conclusions: The data obtained highlight the role of hyperactivity and hyperdopaminergia in DAT-KO rats in spatial learning. We suggest that our findings may help in the further development of new training tasks for individuals with ADHD and spatial memory deficits. Full article

Animals with knockout of the dopamine transporter gene (DAT-KO) display hyperdopaminergic phenotypes, including attention-deficit/hyperactivity-like behaviors. A previous behavioral analysis of heterozygous rats with partial knockout (DAT-HET) suggested increased susceptibility to addictive behaviors. The aim of this study was to investigate elements of addictive behaviors and the mechanisms underlying dopamine release in DAT-HET rats. Offspring derived from DAT-knockout breeding underwent genotyping and behavioral assessment using the marble burying test, a manipulative behavior test using nesting material, and a modified version of the Iowa Gambling Task. Feeding behavior was studied using a binge-eating model. Reinforcing properties were investigated using intracranial self-stimulation under fixed-ratio (FR) and variable-ratio (VR) schedules. Dopamine (DA) release and clearance dynamics were assessed using fast-scan cyclic voltammetry (FSCV). DAT-HET rats exhibited moderate hyperactivity, increased impulsive choice, and compulsive responses. Male DAT-HET rats also showed increased compulsive overeating compared with wild-type (WT) rats of both sexes and female DAT-HET rats. In addition, DAT-HET rats demonstrated a preference for VR self-stimulation, which resembles risk- and thrill-seeking behavior in humans. In DAT-KO rats, impaired DA clearance resulted from complete loss of dopamine transporter function. In DAT-HET rats, increased DA release amplitude was observed, and dopamine persisted longer in the extracellular space than in WT rats. These findings underscore the importance of the DAT-HET model for studying impulsivity, compulsivity, and factors underlying the predisposition to addictive behavior. Full article

Background/Objectives: Chronic ethanol consumption damages erythrocyte membranes, reducing their deformability and disrupting erythropoiesis. Dopaminergic signalling plays an important role in regulating haematopoietic stem cells. However, the impact of genetic alterations in the dopamine system on the functional properties of erythrocytes and their resistance to the toxic effects of alcohol remains understudied. In this study, we evaluated haematological parameters and the sensitivity of erythrocytes to chronic ethanol exposure in DAT-HET rats (heterozygous for the dopamine transporter gene) compared to Wistar rats. Methods: Both lines of rats were subjected to chronic alcoholisation (10% ethanol for six months). Flow cytometry was used to assess reticulocyte production, intracellular esterase activity (cell viability), and membrane lipid asymmetry disruptions. Laser diffraction was used to evaluate osmotic resistance (deformability). Results: The partial knockout of the DAT gene significantly altered the baseline haematological profile, resulting in pronounced leukopenia, moderate thrombocytopenia, moderate erythrocyte macrocytosis, and reduced intracellular esterase activity. The consequences of chronic ethanol consumption in Wistar rats (anaemia, decreased reticulocyte count, increased osmotic rigidity of erythrocytes, and an increased proportion of annexin-positive cells) were similar to those observed in humans, thus confirming the validity of the experimental model. In contrast, chronic alcohol exposure did not significantly influence haematopoiesis parameters or erythrocyte biophysical properties in DAT-HET rats, indicating that even a 50% loss of the dopamine transporter strongly prevented ethanol’s damaging effects on blood cells. Conclusions: The marked contrast between Wistar rats (which develop alcohol-induced anaemia and erythrocyte dysfunction similar to humans) and DAT-HET rats (which remain largely unaffected) demonstrates that dopaminergic signalling plays a previously unrecognised role in determining erythrocyte sensitivity to alcohol toxicity. Full article

Altered mitochondrial function is implicated in disorders characterized by prefrontal cortex activation deficits, including attention deficit hyperactivity disorder (ADHD). The expression of mitochondrial DNA-coded respiratory chain complex I genes (ND1–ND6) in the prefrontal cortex of ADHD animal models was estimated in the present study. ND gene expression was assessed in two publicly available datasets: GSE117357 (Adgrl3 knockout mice) and GSE173926 (MYT1L heterozygous knockout mice). Additionally, we measured NDs gene expression via qPCR in dopamine transporter knockout (DAT-KO) rats and their heterozygous (DAT-Het) littermates. Transcriptomic analysis revealed consistent ND1–ND6 expression profiles across both datasets, and co-expression among ND genes was significantly enhanced in ADHD models compared to wild-type controls. Whole-transcriptome analysis identified associations between ND3 and ND4L expression and genes involved in neural tissue-specific processes, exclusively in ADHD models. In DAT-KO and DAT-Het rats, NDs gene co-expression increased. Furthermore, in DAT-Het rats, which do not exhibit hyperactivity, the upregulation of ND4L expression relative to wild-type littermates was demonstrated. The observed changes in mitochondrial complex I gene co-expression in ADHD models suggest mitochondria may serve as a prospective target for adjuvant therapy. These findings highlight the need for further investigation into mitochondrial contributions to ADHD pathophysiology. Full article

Dopamine transporter (DAT) mutations are associated with neurological and psychiatric diseases, and DAT gene knockout in rats (DAT-KO) provides an opportunity to evaluate the DAT role in pathological conditions. We analyzed DAT expression and co-expression with other genes in the substantia nigra and striatum in public transcriptomic data represented in the GEO repository and then estimated the identified DAT co-expression pattern in DAT-KO rats by RT-PCR. In silico analysis confirmed DAT expression in the substantia nigra and absence of DAT mRNA in the striatum. Also, DAT is co-expressed with genes involved in dopamine signaling, but these associations are disrupted in dopamine neuron-damaging conditions. To estimate this co-expression pattern when DAT expression is lost, we evaluate it in the substantia nigra of DAT-KO rats. However, in DAT-KO rats the associations between genes involved in dopamine signaling were not disturbed compared to wild-type littermates, and tyrosine hydroxylase expression upregulation in the substantia nigra of these animals may be considered as compensation for the loss of dopamine reuptake. Further studies of expression regulation in dopamine neurons of DAT-KO rats may provide valuable information for compensatory mechanisms in substantia nigra dopaminergic neurons. Full article

Background/Objectives: Dopamine dysfunction (DA) is a hallmark of many neurological disorders. In this case, the mechanism of changes in dopamine transmission on behavior remains unclear. This study is a look into the intricate link between disrupted DA signaling, neuronal activity patterns, and behavioral abnormalities in a hyperdopaminergic animal model. Methods: To study the relationship between altered DA levels, neuronal activity, and behavioral deficits, local field potentials (LFPs) were recorded during four different behaviors in dopamine transporter knockout rats (DAT-KO). At the same time, local field potentials were recorded in the striatum and prefrontal cortex. Correlates of LFP and accompanying behavioral patterns in genetically modified (DAT-KO) and control animals were studied. Results: DAT-KO rats exhibited desynchronization between LFPs of the striatum and prefrontal cortex, particularly during exploratory behavior. A suppressive effect of high dopamine levels on the striatum was also observed. Wild-type rats showed greater variability in LFP patterns across certain behaviors, while DAT-KO rats showed more uniform patterns. Conclusions: The decisive role of the synchrony of STR and PFC neurons in the organization of motor acts has been revealed. The greater variability of control animals in certain forms of behavior probably suggests greater adaptability. More uniform patterns in DAT-KO rats, indicating a loss of striatal flexibility when adapting to specific motor tasks. It is likely that hyperdopaminergy in the DAT-KO rat reduces the efficiency of information processing due to less synchronized activity during active behavior. Full article

Playing a key role in the organization of striatal motor output, the dopamine (DA)-ergic system regulates both innate and complex learned behaviors. Growing evidence clearly indicates the involvement of the DA-ergic system in different forms of repetitive (perseverative) behavior. Some of these behaviors accompany such disorders as obsessive–compulsive disorder (OCD), Tourette’s syndrome, schizophrenia, and addiction. In this study, we have traced how the inflexibility of repetitive reactions in the recently developed animal model of hyper-DA-ergia, dopamine transporter knockout rats (DAT-KO rats), affects the realization of innate behavior (grooming) and the learning of spatial (learning and reversal learning in T-maze) and non-spatial (extinction of operant reaction) tasks. We found that the microstructure of grooming in DAT-KO rats significantly differed in comparison to control rats. DAT-KO rats more often demonstrated a fixed syntactic chain, making fewer errors and very rarely missing the chain steps in comparison to control rats. DAT-KO rats’ behavior during inter-grooming intervals was completely different to the control animals. During learning and reversal learning in the T-maze, DAT-KO rats displayed pronounced patterns of hyperactivity and perseverative (stereotypical) activity, which led to worse learning and a worse performance of the task. Most of the DAT-KO rats could not properly learn the behavioral task in question. During re-learning, DAT-KO rats demonstrated rigid perseverative activity even in the absence of any reinforcement. In operant tasks, the mutant rats demonstrated poor extinction of operant lever pressing: they continued to perform lever presses despite no there being reinforcement. Our results suggest that abnormally elevated DA levels may be responsible for behavioral rigidity. It is conceivable that this phenomenon in DAT-KO rats reflects some of the behavioral traits observed in clinical conditions associated with endogenous or exogenous hyper-DA-ergia, such as schizophrenia, substance abuse, OCD, patients with Parkinson disease treated with DA mimetics, etc. Thus, DAT-KO rats may be a valuable behavioral model in the search for new pharmacological approaches to treat such illnesses. Full article

Trace amine-associated receptor 1 (TAAR1) is an attractive target for the design of innovative drugs to be applied in diverse pharmacological settings. Due to a non-negligible structural similarity with endogenous ligands, most of the agonists developed so far resulted in being affected by a low selectivity for TAAR1 with respect to other monoaminergic G protein-coupled receptors, like the adrenoreceptors. This study utilized comparative molecular docking studies and quantitative–structure activity relationship (QSAR) analyses to unveil key structural differences between TAAR1 and alpha2-adrenoreceptor (α₂-ADR), with the aim to design novel TAAR1 agonists characterized by a higher selectivity profile and reduced off-target effects. While the presence of hydrophobic motives is encouraged towards both the two receptors, the introduction of polar/positively charged groups and the ligand conformation deeply affect the TAAR1 or α₂-ADR putative selectivity. These computational methods allowed the identification of the α₂A-ADR agonist guanfacine as an attractive TAAR1-targeting lead compound, demonstrating nanomolar activity in vitro. In vivo exploration of the efficacy of guanfacine showed that it is able to decrease the locomotor activity of dopamine transporter knockout (DAT-KO) rats. Therefore, guanfacine can be considered as an interesting template molecule worthy of structural optimization. The dual activity of guanfacine on both α₂-ADR and TAAR1 signaling and the related crosstalk between the two pathways will deserve more in-depth investigation. Full article

(1) Background: There is an urgent need for effective treatments for cocaine use disorder (CUD), and new pharmacological approaches targeting epigenetic mechanisms appear to be promising options for the treatment of this disease. Dopamine Transporter (DAT) transgenic rats recently have been proposed as a new animal model for studying susceptibility to CUD. (2) Methods: DAT transgenic rats were treated chronically with cocaine (10 mg/kg) for 8 days, and the expression of epigenetic modulators, Lysine Demethylase 6B (KDM6B) and Bromodomain-containing protein 4 (BRD4), was examined in the prefrontal cortex (PFC). (3) Results: We show that only full knockout (KO) of DAT impacts basal levels of KDM6B in females. Additionally, cocaine altered the expression of both epigenetic markers in a sex- and genotype-dependent manner. In response to chronic cocaine, KDM6B expression was decreased in male rats with partial DAT mutation (HET), while no changes were observed in wild-type (WT) or KO rats. Indeed, while HET male rats have reduced KDM6B and BRD4 expression, HET female rats showed increased KDM6B and BRD4 expression levels, highlighting the impact of sex on epigenetic mechanisms in response to cocaine. Finally, both male and female KO rats showed increased expression of BRD4, but only KO females exhibited significantly increased KDM6B expression in response to cocaine. Additionally, the magnitude of these effects was bigger in females when compared to males for both epigenetic enzymes. (4) Conclusions: This preliminary study provides additional support that targeting KDM6B and/or BRD4 may potentially be therapeutic in treating addiction-related behaviors in a sex-dependent manner. Full article

Dopamine (DA) is the critical neurotransmitter involved in the unconscious control of muscle tone and body posture. We evaluated the general motor capacities and muscle responses to postural disturbance in three conditions: normal DA level (wild-type rats, WT), mild DA deficiency (WT after administration of α-methyl-p-tyrosine—AMPT, that blocks DA synthesis), and severe DA depletion (DAT-KO rats after AMPT). The horizontal displacements in WT rats elicited a multi-component EMG corrective response in the flexor and extensor muscles. Similar to the gradual progression of DA-related diseases, we observed different degrees of bradykinesia, rigidity, and postural instability after AMPT. The mild DA deficiency impaired the initiation pattern of corrective responses, specifically delaying the extensor muscles’ activity ipsilaterally to displacement direction and earlier extensor activity from the opposite side. DA depletion in DAT-KO rats after AMPT elicited tremors, general stiffness, and akinesia, and caused earlier response to horizontal displacements in the coactivated flexor and extensor muscles bilaterally. The data obtained show the specific role of DA in postural reactions and suggest that this experimental approach can be used to investigate sensorimotor control in different dopamine-deficient states and to model DA-related diseases. Full article

This article presents a low-cost and flexible software solution for acoustic startle response (ASR) test that can be used with a Spike2-based interface. ASR is a reflexive response to an unexpected, loud acoustic stimulus, and prepulse inhibition (PPI) is a phenomenon in which the startle response is reduced when preceded by a weak prestimulus of the same modality. Measuring PPI is important because changes in PPI have been observed in patients with various psychiatric and neurological disorders. Commercial ASR testing systems are expensive, and their closed source code affects their transparency and result reproducibility. The proposed software is easy to install and use. The Spike2 script is customizable and supports a wide range of PPI protocols. As an example of PPI recording, the article presents data obtained in female rats, both wild-type (WT) and dopamine transporter knockout (DAT-KO), showing the same tendency as the data obtained in males, with ASR on a single pulse higher than ASR on prepulse+pulse, and PPI reduced in DAT-KO rats compared to WT. Full article

Dopamine (DA) and glutamate interact, influencing neural excitability and promoting synaptic plasticity. However, little is known regarding the molecular mechanisms underlying this crosstalk. Since perturbation of DA-AMPA receptor interaction might sustain pathological conditions, the major aim of our work was to evaluate the effect of the hyperactive DA system on the AMPA subunit composition, trafficking, and membrane localization in the prefrontal cortex (PFC). Taking advantage of dopamine transporter knock-out (DAT^−/−) rats, we found that DA overactivity reduced the translation of cortical AMPA receptors and their localization at both synaptic and extra-synaptic sites through, at least in part, altered intracellular vesicular sorting. Moreover, the reduced expression of AMPA receptor-specific anchoring proteins and structural markers, such as Neuroligin-1 and nCadherin, likely indicate a pattern of synaptic instability. Overall, these data reveal that a condition of hyperdopaminergia markedly alters the homeostatic plasticity of AMPA receptors, suggesting a general destabilization and depotentiation of the AMPA-mediated glutamatergic neurotransmission in the PFC. This effect might be functionally relevant for disorders characterized by elevated dopaminergic activity. Full article

Investigation of the precise mechanisms of attention deficit and hyperactivity disorder (ADHD) and other dopamine-associated conditions is crucial for the development of new treatment approaches. In this study, we assessed the effects of repeated and acute administration of α2A-adrenoceptor agonist guanfacine on innate and learned forms of behavior of dopamine transporter knockout (DAT-KO) rats to evaluate the possible noradrenergic modulation of behavioral deficits. DAT-KO and wild type rats were trained in the Hebb–Williams maze to perform spatial working memory tasks. Innate behavior was evaluated via pre pulse inhibition (PPI). Brain activity of the prefrontal cortex and the striatum was assessed. Repeated administration of GF improved the spatial working memory task fulfillment and PPI in DAT-KO rats, and led to specific changes in the power spectra and coherence of brain activity. Our data indicate that both repeated and acute treatment with a non-stimulant noradrenergic drug lead to improvements in the behavior of DAT-KO rats. This study further supports the role of the intricate balance of norepinephrine and dopamine in the regulation of attention. The observed compensatory effect of guanfacine on the behavior of hyperdopaminergic rats may be used in the development of combined treatments to support the dopamine–norepinephrine balance. Full article

Parkinson’s disease is the second most common neurodegenerative pathology. Due to the limitations of existing therapeutic approaches, novel anti-parkinsonian medicines with non-dopamine mechanisms of action are clearly needed. One of the promising pharmacological targets for anti-Parkinson drug development is phosphodiesterase (PDE) 10A. The stimulating motor effects of PDE10A inhibition were detected only under the conditions of partial dopamine depletion. The results raise the question of whether PDE10A inhibitors are able to restore locomotor activity when dopamine levels are very low. To address this issue, we (1) developed and validated the rat model of acute severe dopamine deficiency and (2) tested the action of PDE10A inhibitor MP-10 in this model. All experiments were performed in dopamine transporter knockout (DAT-KO) rats. A tyrosine hydroxylase inhibitor, α-Methyl-DL-tyrosine (αMPT), was used as an agent to cause extreme dopamine deficiency. In vivo tests included estimation of locomotor activity and catalepsy levels in the bar test. Additionally, we evaluated the tissue content of dopamine in brain samples by HPLC analysis. The acute administration of αMPT to DAT-KO rats caused severe depletion of dopamine, immobility, and catalepsy (Dopamine-Deficient DAT-KO (DDD) rats). As expected, treatment with the L-DOPA and carbidopa combination restored the motor functions of DDD rats. Strikingly, administration of MP-10 also fully reversed immobility and catalepsy in DDD rats. According to neurochemical studies, the action of MP-10, in contrast to L-DOPA + carbidopa, seems to be dopamine-independent. These observations indicate that targeting PDE10A may represent a new promising approach in the development of non-dopamine therapies for Parkinson’s disease. Full article