Impramine, fluoxetine and clozapine differently affected reactivity to positive and negative stimuli in a model of motivational anhedonia in rats

Clozapine as a mood stabiliser for schizoaffective disorder: Effectiveness during a three-month follow-up

Clozapine has shown signs of effectiveness in treating symptoms of schizoaffective disorder, although little research has been carried out to specifically assess this question. The objective of this current work was to analyse the mood-stabilising effectiveness and tolerability of clozapine in patients with schizoaffective disorder. This was a prospective, longitudinal, and quasi-experimental trial with three months of follow-up in patients with refractory schizoaffective disorder (PANSS score exceeding 80). Clinical response was evaluated through monthly visits using the YMRS, MADRS, CDSS, CGI-S and UKU. Twenty-seven participants (63% men, 37% women) with a mean age of 32.56 years were included. Clozapine significantly reduced the symptoms of mania, as measured by the YMRS (pre-treatment: 16.19, post-treatment: 0.67; p < 0.01) as well as the symptoms of depression, quantified with the CDSS (pre-treatment: 6.11, post-treatment: 0.67; p < 0.01), MADRS (pre-treatment: 9.56, post-treatment: 1.07; p < 0.01), and CGI-S (pre-treatment: 4.74, post-treatment: 1.15; p < 0.01). The prescription of clozapine significantly reduced the average daily dose of neuroleptics, measured in mg of chlorpromazine (pre-treatment: 1253.55, post-treatment: 742.59; p < 0.01) and hypnosedatives, measured in mg of diazepam (pre-treatment: 33.88, post-treatment: 5.74; p < 0.05) required in these patients. Patient-perceived tolerability, measured with the UKU, also improved during follow-up (pre-treatment: 12.89, post-treatment: 8.14; p < 0.01). The efficacy of clozapine was significant for the affective symptoms of schizoaffective disorder, thereby improving patient tolerability and permitting reductions in the other medications the patients used.

PPARα Signaling: A Candidate Target in Psychiatric Disorder Management

Peroxisome proliferator-activator receptors (PPARs) regulate lipid and glucose metabolism, control inflammatory processes, and modulate several brain functions. Three PPAR isoforms have been identified, PPARα, PPARβ/δ, and PPARγ, which are expressed in different tissues and cell types. Hereinafter, we focus on PPARα involvement in the pathophysiology of neuropsychiatric and neurodegenerative disorders, which is underscored by PPARα localization in neuronal circuits involved in emotion modulation and stress response, and its role in neurodevelopment and neuroinflammation. A multiplicity of downstream pathways modulated by PPARα activation, including glutamatergic neurotransmission, upregulation of brain-derived neurotrophic factor, and neurosteroidogenic effects, encompass mechanisms underlying behavioral regulation. Modulation of dopamine neuronal firing in the ventral tegmental area likely contributes to PPARα effects in depression, anhedonia, and autism spectrum disorder (ASD). Based on robust preclinical evidence and the initial results of clinical studies, future clinical trials should assess the efficacy of PPARα agonists in the treatment of mood and neurodevelopmental disorders, such as depression, schizophrenia, and ASD.

Targeting PPARα in the rat valproic acid model of autism: focus on social motivational impairment and sex-related differences

BACKGROUND

The social motivational theory of autism spectrum disorder (ASD) focuses on social anhedonia as key causal feature of the impaired peer relationships that characterize ASD patients. ASD prevalence is higher in boys, but increasing evidence suggests underdiagnosis and undertreatment in girls. We showed that stress-induced motivational anhedonia is relieved by repeated treatment with fenofibrate (FBR), a peroxisome proliferator-activated receptor α (PPARα) agonist. Here, we used the valproic acid (VPA) model of ASD in rats to examine male and female phenotypes and assess whether FBR administration from weaning to young adulthood relieved social impairments.

METHODS

Male and female rats exposed to saline or VPA at gestational day 12.5 received standard or FBR-enriched diet from postnatal day 21 to 48-53, when behavioral tests and ex vivo neurochemical analyses were performed. Phosphorylation levels of DARPP-32 in response to social and nonsocial cues, as index of dopamine D1 receptor activation, levels of expression of PPARα, vesicular glutamatergic and GABAergic transporters, and postsynaptic density protein PSD-95 were analyzed by immunoblotting in selected brain regions.

RESULTS

FBR administration relieved social impairment and perseverative behavior in VPA-exposed male and female rats, but it was only effective on female stereotypies. Dopamine D1 receptor signaling triggered by social interaction in the nucleus accumbens shell was blunted in VPA-exposed rats, and it was rescued by FBR treatment only in males. VPA-exposed rats of both sexes exhibited an increased ratio of striatal excitatory over inhibitory synaptic markers that was normalized by FBR treatment.

LIMITATIONS

This study did not directly address the extent of motivational deficit in VPA-exposed rats and whether FBR administration restored the likely decreased motivation to operate for social reward. Future studies using operant behavior protocols will address this relevant issue.

CONCLUSIONS

The results support the involvement of impaired motivational mechanisms in ASD-like social deficits and suggest the rationale for a possible pharmacological treatment. Moreover, the study highlights sex-related differences in the expression of ASD-like symptoms and their differential responses to FBR treatment.

Adaptive mechanisms following antidepressant drugs: Focus on serotonin 5-HT2A receptors

BACKGROUND

There is a strong support for the role of serotonin (5-HT) neurotransmission in depression and in the mechanism of action of antidepressants. Among 5-HT receptors, 5-HT2A receptor subtype seems to be an important target implicated in the above disorder.

METHODS

The aim of the study was to investigate the effects of antidepressants, such as imipramine (15 mg/kg), escitalopram (10 mg/kg) and tianeptine (10 mg/kg) as well as drugs with antidepressant activity, including N-acetylcysteine (100 mg/kg) and URB597 (a fatty acid amide hydrolase inhibitor, 0.3 mg/kg) on the 5-HT2A receptor labeling pattern in selected rat brain regions. Following acute or chronic (14 days) drug administration, rat brains were analyzed by using autoradiography with the 5-HT2A receptor antagonist [3H]ketanserin.

RESULTS

Single dose or chronic administration of imipramine decreased the radioligand binding in the claustrum and cortical subregions. The [3H]ketanserin binding either increased or decreased in cortical areas after acute N-acetylcysteine and URB597 administration, respectively. A similar shift towards reduction of the [3H]ketanserin binding was detected in the nucleus accumbens shell following either acute treatment with imipramine, escitalopram, N-acetylcysteine and URB597 or repeated administration of imipramine, tianeptine and URB597.

CONCLUSIONS

In conclusion, the present result indicate different sensitivity of brain 5-HT2A receptors to antidepressant drugs depending on schedule of drug administration and rat brain regions. The decrease of accumbal shell 5-HT2A receptor labeling by antidepressant drugs exhibiting different primary mechanism of action seems to be a common targeting mechanism associated with the outcome of depression treatment.

Anhedonia across borders: Transdiagnostic relevance of reward dysfunction for noninvasive brain stimulation endophenotypes

INTRODUCTION

Anhedonia is a transdiagnostic psychopathological dimension, consisting in the impaired ability to experience pleasure. In order to further our understanding of its neural correlates and to explore its potential relevance as a predictor of treatment response, in this article we systematically reviewed studies involving anhedonia and neuromodulation interventions, across different disorders.

METHODS

We included seven studies fulfilling inclusion/exclusion criteria and involving different measures of anticipatory and consummatory anhedonia, as well as different noninvasive brain stimulation interventions (transcranial magnetic stimulation and transcranial direct current stimulation). Studies not exploring hedonic measures or not involving neuromodulation intervention were excluded.

RESULTS

All the included studies entailed the use of rTMS protocols in one of the diverse prefrontal targets. The limited amount of studies and the heterogeneity of stimulation protocols did not allow to draw any conclusion with regard to the efficacy of rTMS in the treatment of transnosographic anhedonia. A potential for anhedonia in dissecting possible endophenotypes of different psychopathological conditions preliminarily emerged.

CONCLUSIONS

Anhedonia is an underexplored condition in neuromodulation trials. It may represent a valuable transdiagnostic dimension that requires further examination in order to discover new clinical predictors for treatment response.

Unlimited sucrose consumption during adolescence generates a depressive-like phenotype in adulthood

Depression is highly prevalent worldwide, but its etiology is not fully understood. An overlooked possible contributor to the epidemic of depression is feeding styles, particularly at early age when the brain is intensely changing. We have previously reported that unlimited sucrose consumption during adolescence leads to enduring changes in brain reward function. Here, we tested the hypothesis that sucrose consumption during adolescence would lead to a 'depressive-like' phenotype. Adolescent male rats were given unlimited access to 5% sucrose in their home cages from postnatal day 30 to postnatal day 46 and their emotional behavior was subsequently examined at adulthood. Sucrose consumption during adolescence caused anhedonia, decreased motivation for saccharin, increased immobility in the forced swim test and exacerbated anxiety-like behavior. Additionally, sucrose consumption during adolescence decreased cell proliferation in the hippocampus in adulthood. Chronic treatment with imipramine (10 mg/kg) normalized behavior and restored cell proliferation in the hippocampus of adult rats with a history of sucrose consumption during adolescence. A similar sucrose consumption starting at adulthood only increases immobility in the forced swim test, suggesting that sucrose intake affects also adults' behavior but to a lesser degree. Overall, our findings reveal an unsuspected protracted effect of sucrose consumption on behavior and suggest that unlimited sucrose consumption during critical periods of brain development may play an important role in the etiology of reward-related disorders such as depression.

DARPP-32 in the orchestration of responses to positive natural stimuli

Dopamine- and cAMP-regulated phosphoprotein (M_r 32 kDa, DARPP-32) is an integrator of multiple neuronal signals and plays a crucial role particularly in mediating the dopaminergic component of the systems involved in the evaluation of stimuli and the ensuing elaboration of complex behavioral responses (e.g., responses to reinforcers and stressors). Dopamine neurons can fire tonically or phasically in distinct timescales and in specific brain regions to code different behaviorally relevant information. Dopamine signaling is mediated mainly through the regulation of adenylyl cyclase activity, stimulated by D1-like or inhibited by D2-like receptors, respectively, that modulates cAMP-dependent protein kinase (PKA) function. The activity of DARPP-32 is finely regulated by its phosphorylation at multiple sites. Phosphorylation at the threonine (Thr) 34 residue by PKA converts DARPP-32 into an inhibitor of protein phosphatase 1, while the phosphorylation at the Thr75 residue turns it into an inhibitor of PKA. Thus, DARPP-32 is critically implicated in regulating striatal output in response to the convergent pathways that influence signaling of the cAMP/PKA pathway. This review summarizes some of the landmark and recent studies of DARPP-32-mediated signaling in the attempt to clarify the role played by DARPP-32 in the response to rewarding natural stimuli. Particularly, the review deals with data derived from rodents studies and discusses the involvement of the cAMP/PKA/DARPP-32 pathway in: 1) appetitive food-sustained motivated behaviors, 2) motivated behaviors sustained by social reward, 3) sexual behavior, and 4) responses to environmental enrichment.

Antidepressant and pro-motivational effects of repeated lamotrigine treatment in a rat model of depressive symptoms

Background

Methods

Results

Limitations

Conclusions

Making Sense of Rodent Models of Anhedonia

A markedly reduced interest or pleasure in activities previously considered pleasurable is a main symptom in mood disorder and psychosis and is often present in other psychiatric disorders and neurodegenerative diseases. This condition can be labeled as "anhedonia," although in its most rigorous connotation the term refers to the lost capacity to feel pleasure that is one aspect of the complex phenomenon of processing and responding to reward. The responses to rewarding stimuli are relatively easy to study in rodents, and the experimental conditions that consistently and persistently impair these responses are used to model anhedonia. To this end, long-term exposure to environmental aversive conditions is primarily used, and the resulting deficits in reward responses are often accompanied by other deficits that are mainly reminiscent of clinical depressive symptoms. The different components of impaired reward responses induced by environmental aversive events can be assessed by different tests or protocols that require different degrees of time allocation, technical resources, and equipment. Rodent models of anhedonia are valuable tools in the study of the neurobiological mechanisms underpinning impaired behavioral responses and in the screening and characterization of drugs that may reverse these behavioral deficits. In particular, the antianhedonic or promotivational effects are relevant features in the spectrum of activities of drugs used in mood disorders or psychosis. Thus, more than the model, it is the choice of tests that is crucial since it influences which facets of anhedonia will be detected and should be tuned to the purpose of the study.

Aripiprazole relieves motivational anhedonia in rats

BACKGROUND

Anhedonia is considered a relevant feature in depression and psychosis, characterized by poor treatment outcome, and associated with deficits in mesolimbic dopaminergic responsiveness. Clinical studies suggest the potential utility of aripiprazole as adjunctive therapy for resistant depression. Since aripiprazole can stabilize the dopaminergic system, in search of tailored therapeutic strategies for reward dysfunctions, we investigated whether the drug restored motivation toward positive stimuli in a rat model.

METHODS

Anhedonia is modeled in non food-deprived 9-week old male Sprague-Dawley rats by exposing them to a chronic unavoidable stress protocol, consisting in repeated exposure to tail-shock or restrain, which disrupts the motivation to acquire a reward-directed behavior and the competence to escape aversive stimuli. We evaluated whether long-term aripiprazole administration (1mg/kg/day, i.p.) restored in chronically stressed rats, a) the disrupted dopaminergic response to sucrose consumption measuring DARPP-32 phosphorylation levels in the nucleus accumbens shell by immunoblotting; b) the motivation to operate in a sucrose self-administration protocol.

RESULTS

Long-term aripiprazole administration restored DARPP-32 phosphorylation changes in response to sucrose and reinstated the motivational drive to acquire the reward in the progressive ratio task. However, it did not restore reactivity to aversive stimuli.

LIMITATIONS

The results obtained in our model may not fully translate to the clinic, as anhedonia is a complex construct in patients, where motivational aspects represent a central but not unique feature.

CONCLUSIONS

This study demonstrates that aripiprazole relieved motivational anhedonia in a stress-induced model and warrants further studies to ascertain whether this activity is clinically relevant for antipsychotic or adjunctive antidepressant treatments.

Stereological Study on the Positive Effect of Running Exercise on the Capillaries in the Hippocampus in a Depression Model

Running exercise is an effective method to improve depressive symptoms when combined with drugs. However, the underlying mechanisms are not fully clear. Cerebral blood flow perfusion in depressed patients is significantly lower in the hippocampus. Physical activity can achieve cerebrovascular benefits. The purpose of this study was to evaluate the impacts of running exercise on capillaries in the hippocampal CA1 and dentate gyrus (DG) regions. The chronic unpredictable stress (CUS) depression model was used in this study. CUS rats were given 4 weeks of running exercise from the fifth week to the eighth week (20 min every day from Monday to Friday each week). The sucrose consumption test was used to measure anhedonia. Furthermore, stereological methods were used to investigate the capillary changes among the control group, CUS/Standard group and CUS/Running group. Sucrose consumption significantly increased in the CUS/Running group. Running exercise has positive effects on the capillaries parameters in the hippocampal CA1 and DG regions, such as the total volume, total length and total surface area. These results demonstrated that capillaries are protected by running exercise in the hippocampal CA1 and DG might be one of the structural bases for the exercise-induced treatment of depression-like behavior. These results suggest that drugs and behavior influence capillaries and may be considered as a new means for depression treatment in the future.

Considerations on nonclinical approaches to modeling risk factors of suicidal ideation and behavior

Given the serious nature of suicidal ideation and behavior (SIB) and the possibility of treatment-emergent SIB, pharmaceutical companies are now applying more proactive approaches in clinical trials and are considering the value of nonclinical models to predict SIB. The current review summarizes nonclinical approaches to modeling three common risk factors associated with SIB: aggression, impulsivity, and anhedonia. For each risk factor, a general description, advantages and disadvantages, species considerations, nonclinical to clinical translation, and pharmacological validation with respect to treatments associated with SIB are summarized. From this review, several gaps were identified that need to be addressed before use of these nonclinical models can be considered a viable option to predict the relative risk for SIB. Other future directions that may compliment these nonclinical approaches, including the use of selectively-bred or genetically-modified rodent models, transgenic models, gene expression profiling, and biomarker analysis, are discussed. This article was developed with the support of the DruSafe Leadership Group of the International Consortium for Innovation and Quality in Pharmaceutical Development (IQ, www.iqconsortium.org).

A comparison of methods for the analysis of binomial clustered outcomes in behavioral research

BACKGROUND

In behavioral research, data consisting of a per-subject proportion of "successes" and "failures" over a finite number of trials often arise. This clustered binary data are usually non-normally distributed, which can distort inference if the usual general linear model is applied and sample size is small. A number of more advanced methods is available, but they are often technically challenging and a comparative assessment of their performances in behavioral setups has not been performed.

METHOD

We studied the performances of some methods applicable to the analysis of proportions; namely linear regression, Poisson regression, beta-binomial regression and Generalized Linear Mixed Models (GLMMs). We report on a simulation study evaluating power and Type I error rate of these models in hypothetical scenarios met by behavioral researchers; plus, we describe results from the application of these methods on data from real experiments.

RESULTS

Our results show that, while GLMMs are powerful instruments for the analysis of clustered binary outcomes, beta-binomial regression can outperform them in a range of scenarios. Linear regression gave results consistent with the nominal level of significance, but was overall less powerful. Poisson regression, instead, mostly led to anticonservative inference.

COMPARISON WITH EXISTING METHODS

GLMMs and beta-binomial regression are generally more powerful than linear regression; yet linear regression is robust to model misspecification in some conditions, whereas Poisson regression suffers heavily from violations of the assumptions when used to model proportion data.

CONCLUSIONS

We conclude providing directions to behavioral scientists dealing with clustered binary data and small sample sizes.

The protective effect of Hypericum connatum on stress-induced escape deficit in rat is related to its flavonoid content

Context Hypericum perforatum L. (Hypericaceae), used in moderate depression treatment, is active in experimental tests for antidepressant activity. For H. connatum Lam., a South American species lacking hyperforin, antidepressant effects have not been demonstrated. Objective This study evaluates the antidepressant-like effect of H. connatum in rats and identifies the components involved in this activity. Materials and methods First, the effects of acute and 14-d oral administrations of an extract derived from H. connatum aerial parts were studied using the Escape Deficit (ED) test. Next, methanol-extracted flavonoid-enriched fractions B and C and fraction-purified flavonoids (quercetin, rutin and isoquercitrin) were evaluated in the ED test after acute administration. To rule out possible confounding effects of the flavonoids, we examined nociceptive threshold using the tail-flick test and anxious behaviour using the elevated plus maze (EPM) test. Results Hypericum connatum increased reactivity of unavoidable stress-exposed rats after acute (0.5 and 1 g/kg: ED = 18.6/30 and 19.8/30, respectively) and repeated administration (0.5 g/kg twice daily: ED = 17.8/30). Protective effects were observed for fractions B and C (250 mg/kg: ED = 18.1/30 and 18.8/30, respectively), quercetin (2.5, 5 and 10 mg/kg: ED = 15.3/30, 18.3/30 and 21.6/30, respectively), rutin (5 and 10 mg/kg: ED = 15.4/30 and 13.0/30, respectively) and isoquercitrin (2.5 mg/kg: ED = 19.2/30). The flavonoids did not modify nociceptive threshold or performance in the EPM test. Discussion and conclusion Hypericum connatum showed protective activity in the ED test, a correlate of potential antidepressant-like effects that appeared to be related to the flavonoid components of this species.

PPARα modulation of mesolimbic dopamine transmission rescues depression-related behaviors

Depressive disorders cause a substantial burden for the individual and the society. Key depressive symptoms can be modeled in animals and enable the development of novel therapeutic interventions. Chronic unavoidable stress disrupts rats' competence to escape noxious stimuli and self-administer sucrose, configuring a depression model characterized by escape deficit and motivational anhedonia associated to impaired dopaminergic responses to sucrose in the nucleus accumbens shell (NAcS). Repeated treatments that restore these responses also relieve behavioral symptoms. Ventral tegmental area (VTA) dopamine neurons encode reward and motivation and are implicated in the neuropathology of depressive-like behaviors. Peroxisome proliferator-activated receptors type-α (PPARα) acutely regulate VTA dopamine neuron firing via β2 subunit-containing nicotinic acetylcholine receptors (β2*nAChRs) through phosphorylation and this effect is predictive of antidepressant-like effects. Here, by combining behavioral, electrophysiological and biochemical techniques, we studied the effects of repeated PPARα stimulation by fenofibrate on mesolimbic dopamine system. We found decreased β2*nAChRs phosphorylation levels and a switch from tonic to phasic activity of dopamine cells in the VTA, and increased phosphorylation of dopamine and cAMP-regulated phosphoprotein Mr 32,000 (DARPP-32) in the NAcS. We then investigated whether long-term fenofibrate administration to stressed rats reinstated the decreased DARPP-32 response to sucrose and whether this effect translated into antidepressant-like properties. Fenofibrate restored dopaminergic responses to appetitive stimuli, reactivity to aversive stimuli and motivation to self-administer sucrose. Overall, this study suggests PPARα as new targets for antidepressant therapies endowed with motivational anti-anhedonic properties, further supporting the role of an unbalanced mesolimbic dopamine system in pathophysiology of depressive disorders.

Diminished effort on a progressive ratio task in both unipolar and bipolar depression

BACKGROUND

Amotivation, or decisional anhedonia, is a prominent and disabling feature of depression. However, this aspect of depression remains understudied, and no prior work has applied objective laboratory tests of motivation in both unipolar and bipolar depression.

METHODS

We assessed motivation deficits using a Progressive Ratio Task (PRT) that indexes willingness to exert effort for monetary reward. The PRT was administered to 96 adults ages 18-60 including 25 participants with a current episode of unipolar depression, 28 with bipolar disorder (current episode depressed), and 43 controls without any Axis I psychiatric disorders.

RESULTS

Depressed participants exhibited significantly lower motivation than control participants as objectively defined by progressive ratio breakpoints. Both the unipolar and bipolar groups were lower than controls but did not differ from each other.

LIMITATIONS

Medication use differed across groups, and we did not have a separate control task to measure psychomotor activity; however neither medication effects or psychomotor slowing are likely to explain our findings.

CONCLUSIONS

Our study fills an important gap in the literature by providing evidence that diminished effort on the PRT is present across depressed patients who experience either unipolar or bipolar depression. This adds to growing evidence for shared mechanisms of reward and motivation dysfunction, and highlights the importance of improving the assessment and treatment of motivation deficits across the mood disorders spectrum.

Running exercise protects the capillaries in white matter in a rat model of depression

Running has been shown to improve depressive symptoms when used as an adjunct to medication. However, the mechanisms underlying the antidepressant effects of running are not fully understood. Changes of capillaries in white matter have been discovered in clinical patients and depression model rats. Considering the important part of white matter in depression, running may cause capillary structural changes in white matter. Chronic unpredictable stress (CUS) rats were provided with a 4-week running exercise (from the fifth week to the eighth week) for 20 minutes each day for 5 consecutive days each week. Anhedonia was measured by a behavior test. Furthermore, capillary changes were investigated in the control group, the CUS/Standard group, and the CUS/Running group using stereological methods. The 4-week running increased sucrose consumption significantly in the CUS/Running group and had significant effects on the total volume, total length, and total surface area of the capillaries in the white matter of depression rats. These results demonstrated that exercise-induced protection of the capillaries in white matter might be one of the structural bases for the exercise-induced treatment of depression. It might provide important parameters for further study of the vascular mechanisms of depression and a new research direction for the development of clinical antidepressant means. J. Comp. Neurol. 524:3577-3586, 2016. © 2016 Wiley Periodicals, Inc.

Stathmin reduction and cytoskeleton rearrangement in rat nucleus accumbens in response to clozapine and risperidone treatment - Comparative proteomic study

The complex network of anatomical connections of the nucleus accumbens (NAc) makes it an interface responsible for the selection and integration of cognitive and affective information to modulate appetitive or aversively motivated behaviour. There is evidence for NAc dysfunction in schizophrenia. NAc also seems to be important for antipsychotic drug action, but the biochemical characteristics of drug-induced alterations within NAc remain incompletely characterized. In this study, a comprehensive proteomic analysis was performed to describe the differences in the mechanisms of action of clozapine (CLO) and risperidone (RIS) in the rat NAc. Both antipsychotics influenced the level of microtubule-regulating proteins, i.e., stathmin, and proteins of the collapsin response mediator protein family (CRMPs), and only CLO affected NAD-dependent protein deacetylase sirtuin-2 and septin 6. Both antipsychotics induced changes in levels of other cytoskeleton-related proteins. CLO exclusively up-regulated proteins involved in neuroprotection, such as glutathione synthetase, heat-shock 70-kDa protein 8 and mitochondrial heat-shock protein 75. RIS tuned cell function by changing the pattern of post-translational modifications of some proteins: it down-regulated the phosphorylated forms of stathmin and dopamine and the cyclic AMP-regulated phosphoprotein (DARPP-32) isoform but up-regulated cyclin-dependent kinase 5 (Cdk5). RIS modulated the level and phosphorylation state of synaptic proteins: synapsin-2, synaptotagmin-1 and adaptor-related protein-2 (AP-2) complex.

The Role of Dopamine and Its Dysfunction as a Consequence of Oxidative Stress

Dopamine is a neurotransmitter that is produced in the substantia nigra, ventral tegmental area, and hypothalamus of the brain. Dysfunction of the dopamine system has been implicated in different nervous system diseases. The level of dopamine transmission increases in response to any type of reward and by a large number of strongly additive drugs. The role of dopamine dysfunction as a consequence of oxidative stress is involved in health and disease. Introduce new potential targets for the development of therapeutic interventions based on antioxidant compounds. The present review focuses on the therapeutic potential of antioxidant compounds as a coadjuvant treatment to conventional neurological disorders is discussed.