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Opioid withdrawal produces sex-specific effects on fentanyl-vs.-food choice and mesolimbic transcription

ABSTRACT: Background: Opioid withdrawal is a key driver of opioid addiction and an obstacle to recovery. However, withdrawal effects on opioid reinforcement and mesolimbic neuroadaptation are understudied and the role of sex is largely unknown. Methods: Male (n=13) and female (n=12) rats responded under a fentanyl-vs.-food “choice” procedure during daily 2h sessions. In addition to the daily choice sessions, rats were provided extended access to fentanyl during 12h self-administration sessions. After two weeks of this selfadministration regimen, the nucleus accumbens (NAc) and ventral tegmental area (VTA) of a subset of rats were subjected to RNA sequencing. In the remaining rats, a third week of this self-administration regimen was conducted, during which methadone effects on fentanyl-vs.-food choice were determined. Results: Prior to opioid dependence, male and female rats similarly allocated responding between fentanyl and food. Abstinence from extended fentanyl access elicited similar increases in somatic withdrawal signs in both sexes. Despite similar withdrawal signs and extended access fentanyl intake, opioid withdrawal was accompanied by a maladaptive increase in fentanyl choice in males, but not females. Behavioral sex differences corresponded with a greater number of differentially expressed genes in the NAc and VTA of opioidwithdrawn females relative to males. Methadone blocked withdrawal-associated increases in fentanyl choice in males, but failed to further decrease fentanyl choice in females. Conclusions: These results provide foundational evidence of sex-specific neuroadaptations to opioid withdrawal, which may be relevant to the female-specific resilience to withdrawal-associated increases in opioid choice and aid in the identification of novel therapeutic targets.

ORGANISM(S): Rattus norvegicus

PROVIDER: GSE173959 | GEO | 2021/05/06

REPOSITORIES: GEO

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Project description:The objective of this study was to determine changes in gene expression in the ventral tegmental area (VTA) following loss-of-control alcohol drinking by alcohol-preferring (P) rats. Adult female P rats (n = 7) were given concurrent access to 10, 20 and 30% EtOH for four 1-hr sessions daily for 10 weeks followed by 2 cycles of 2 weeks of abstinence and 2 weeks of EtOH access. Rats were killed by decapitation 3 hr after the 4th daily EtOH-access session at the end of the second 2-week relapse period. An age-matched water control group of female P rats (n = 8) was also killed. RNA was prepared from micropunch samples of the VTA from individual rats; analyses were conducted with Affymetrix Rat 230.2 chips. Ethanol intakes were 1.5-2.5 g/kg per sessions, resulting in blood levels >200 mg% at the end of the 4th session. There were 211 named genes that were significantly different (FDR = 0.1) between the water and EtOH groups. Bioinformatics analyses indicated alterations in (a) transcription factors that reduced excitation-coupled transcription and promoted exocitotic neuronal damage involving clusters of genes associated with Nfkbia, Fos and Srebf1; (b) genes that reduced cholesterol and fatty acid synthesis, and increased protein degradation; and (c) genes involved in cell-to-cell interactions and regulation of the actin cytoskeleton. Among the named genes, there were 62 genes in common with differences between alcohol-naïve P and non-preferring (NP) rats, with 43 of the genes changing in the opposite direction following excessive binge-like drinking. These genes are involved in a pro-inflammatory response, and enhanced response to glucocorticoids and steroid hormones. Overall, the results of this study indicated that excessive binge-like alcohol drinking by P rats may be altering the expression of genes that promote neuronal damage. Comparison of Differences in Gene Expression in the Ventral Tegmental Area of Rat Lines Selectively Bred for High or Low Alcohol Consumption

Project description:Here, we identify persistent and substantial variation in ethanol drinking behavior within an inbred mouse strain and utilize this model to identify gene networks influencing such non-genetic variation in ethanol intake. C57BL/6NCrl mice showed persistent inter-individual variation of ethanol intake in a two-bottle choice paradigm over a three week period, ranging from less than 1 g/kg to over 14 g/kg ethanol in an 18h interval. Whole genome microarray expression analysis in nucleus accumbens, prefrontal cortex and ventral tegmental area of individual animals identified gene expression patterns correlated with ethanol intake. Results included several gene networks previously implicated in ethanol behaviors, such as glutamate signaling, BDNF and genes involved in synaptic vesicle function. Additionally, genes functioning in epigenetic chromatin or DNA modifications such as acetylation and/or methylation also had expression patterns correlated with ethanol intake. Our results thus implicate specific brain regional gene networks, including chromatin modification factors, as potentially important mechanisms underlying individual variation in ethanol intake. Voluntary two-bottle choice drinking was performed as described previously (Khisti et al. 2006). Briefly, two bottles containing 10%(w/v) ethanol (Aaper Alcohol and Chemical Co. Shelbyville, KY) or tap water were placed into the home cage at the beginning of the dark cycle. Tube position was varied every two days (L, L, R, R). Drinking sessions lasted 18 hours/day followed by 6 hours access to water only. Mice had four consecutive drinking sessions followed by four days of abstinence repeated four times to give 16 total drinking sessions. Three brain regions were harvested 6 days after the last drinking session: prefrontal cortex (PFC), nucleus accumbens (NAc) and ventral tegmental area (VTA) as previously described (Kerns et al. 2005). Labeled cRNA from individual animals (n=19) was hybridized to a single microarray for each brain region (n=58 total microarrays).

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Opioid withdrawal produces sex-specific effects on fentanyl-vs.-food choice and mesolimbic transcription

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