Dataset Information

Anhedonia, Reduced Cocaine Reward, and Dopamine Dysfunction in a Rat Model of Posttraumatic Stress Disorder.

ABSTRACT: Posttraumatic stress disorder (PTSD) co-occurs with substance use disorders at high rates, but the neurobiological basis of this relationship is largely unknown. PTSD and drug addiction each involve dysregulation of brain reward circuitry; therefore, the identification of pathology of the mesolimbic dopamine system may aid in understanding their functional relationship. Dopamine reward dysfunction also may be relevant to the mechanisms underlying the PTSD symptoms of anhedonia and emotional numbing.Single-prolonged stress (SPS) was used as a rat model of PTSD, and a series of behavioral and neuropharmacologic assays were applied to assess the impact of SPS on reward, cocaine intake, and components of the striatal dopamine system.Exposure to SPS increased anhedonia-like behaviors and decreased the rewarding properties of cocaine compared with control handling. Altered cocaine intake during extended access self-administration sessions was observed in rats exposed to SPS, further suggesting a difference in the reinforcing properties of cocaine following severe stress. SPS reduced tissue content of dopamine and its metabolites in the striatum, as well as altered striatal dopamine transporter and D2, but not D1, receptor densities.These results support a role for altered dopaminergic transmission in reduced reward function in PTSD. Pathology of the dopamine system and the degradation of reward processes may contribute to PTSD symptomology and have implications for co-occurring psychiatric disorders such as substance abuse or depression.

SUBMITTER: Enman NM

PROVIDER: S-EPMC4644715 | biostudies-literature | 2015 Dec

REPOSITORIES: biostudies-literature

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Anhedonia, Reduced Cocaine Reward, and Dopamine Dysfunction in a Rat Model of Posttraumatic Stress Disorder.

Enman Nicole M NM Arthur Kayti K Ward Sara J SJ Perrine Shane A SA Unterwald Ellen M EM

Biological psychiatry 20150506 12

<h4>Background</h4>Posttraumatic stress disorder (PTSD) co-occurs with substance use disorders at high rates, but the neurobiological basis of this relationship is largely unknown. PTSD and drug addiction each involve dysregulation of brain reward circuitry; therefore, the identification of pathology of the mesolimbic dopamine system may aid in understanding their functional relationship. Dopamine reward dysfunction also may be relevant to the mechanisms underlying the PTSD symptoms of anhedonia ...[more]

PMID: 26115790

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Project description:Treatments for Cocaine Use Disorder (CUD) are variably effective, and there are no FDA-approved medications. One approach to developing new treatments for CUD may be to investigate and target poor prognostic signs. One such sign is anhedonia (i.e. a loss of pleasure or interest in non-drug rewards), which predicts worse outcomes in existing CUD treatments. Inflammation is thought to underlie anhedonia in many other disorders, but the relationship between anhedonia and inflammation has not been investigated in CUD. Therefore, we assessed peripheral genome-wide gene expression in n = 48 individuals with CUD with high (n = 24) vs. low (n = 24) levels of anhedonia, defined by a median split of self-reported anhedonia. Our hypothesis was that individuals with high anhedonia would show differential gene expression in inflammatory pathways. No individual genes were significantly different between the low and high anhedonia groups when using t-tests with a stringent false discovery rate correction (FDR-corrected p < 0.05). However, an exploratory analysis identified 166 loci where t-tests suggested group differences at a nominal p < 0.05. We used DAVID, a bioinformatics tool that provides functional interpretations of complex lists of genes, to examine representation of this gene list in known pathways. It confirmed that mechanisms related to immunity were the top significant associations with anhedonia in the sample. Further, the two top differentially expressed genes in our sample, IRF1 and GBP5, both have primary inflammation and immune functions, and were significantly negatively correlated with total scores on our self-report of anhedonia across all 48 subjects. These results suggest that prioritizing development of anti-inflammatory medications for CUD may pay dividends, particularly in combination with treatment-matching strategies using either phenotypic measures of anhedonia or biomarkers of inflammatory gene expression to individualize treatment.

Project description:An inhibited neural response to reward is typical of clinical depression and can predict an individual's overall depressive symptoms. However, the mechanism underlying this are unclear. Previous studies have found that anhedonia and inattention may mediate the relationship between reward sensitivity and depressive symptoms. Therefore, this study aimed to verify the relationship between reward sensitivity and overall depressive symptoms in a depressive tendency sample as well as to explore the mechanism underlying the ability of neural responses to reward to predict overall depressive symptoms via a mediation model. Sixty-four participants (33 with depressive tendencies and 31 without; dichotomized by BDI-II) finished simple gambling tasks while their event-related potential components (ERPs) were recorded and compared. Linear regression was conducted to verify the predictive effect of ERPs on overall depressive symptoms. A multiple mediator model was used, with anhedonia and distractibility as mediators reward sensitivity and overall depressive symptoms. The amplitude of reward positivity (ΔRewP) was greater in healthy controls compared to those with depressive tendencies (p = 0.006). Both the gain-locked ERP component (b = - 1.183, p = 0.007) and the ΔRewP (b = - 0.991, p = 0.024) could significantly negatively predict overall depressive symptoms even after controlling for all anxiety symptoms. The indirect effects of anhedonia and distractibility were significant (both confidence intervals did not contain 0) while the direct effect of reward sensitivity on depressive symptom was not significant (lower confidence interval = - 0.320, upper confidence interval = 0.065). Individuals with depressive tendencies display impaired neural responses to reward compared to healthy controls and reduced individual neural responses to reward may reflect the different biotypes of depression such as anhedonia and inattention.

Dataset Information

Anhedonia, Reduced Cocaine Reward, and Dopamine Dysfunction in a Rat Model of Posttraumatic Stress Disorder.

Publications

Anhedonia, Reduced Cocaine Reward, and Dopamine Dysfunction in a Rat Model of Posttraumatic Stress Disorder.

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