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Cocaine self-administration alters transcriptome-wide responses in the brain's reward circuitry

ABSTRACT: Global changes in gene expression that underlie the circuit and behavioral dysregulation associated with cocaine addiction remain incompletely understood. Here, we determined how a history of cocaine self-administration (SA) “re-programs” transcriptome-wide responses at baseline and in response to cocaine re-exposure after prolonged withdrawal (WD). We assigned male mice to one of six groups: saline or cocaine SA + 24 hr WD; or saline/cocaine SA + 30 d WD + an acute saline/cocaine challenge within the previous drug-paired context. RNA-seq was then conducted on six interconnected brain reward regions. We focused on patterns of gene expression that were altered by cocaine SA, in particular, molecular targets that show priming or desensitization upon re-exposure to cocaine. Genes that were affected uniquely by acute cocaine after cocaine SA+WD displayed region-specific regulation. The greatest number of regulated genes were seen in nucleus accumbens, dorsal striatum, and basolateral amygdala. Further analysis revealed several transcription factors as key upstream regulators in these three regions, including several not previously implicated in cocaine action. Regulation of subsets of these primed and desensitized genes correlated robustly with SA behavior displayed by individual mice. For example, analysis of transcriptome-wide expression changes revealed that genes associated with cocaine intake respond to contextual information in a region-specific manner. This comprehensive picture of transcriptome-wide regulation by cocaine SA and WD throughout the brain’s reward circuitry provides new insight into the molecular basis of cocaine addiction, which will guide future studies of the key molecular pathways involved.

ORGANISM(S): Mus musculus

PROVIDER: GSE110344 | GEO | 2018/08/22

REPOSITORIES: GEO

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Project description:By using high-density oligonucleotide arrays, we profiled gene expression in reward-related brain regions of rats that developed escalated cocaine intake after extended access to cocaine (6 h per day). Rats allowed restricted daily access to cocaine (only 1 h) that displayed a stable level of cocaine intake and cocaine naive rats were used for controls. Four analysis methods were compared: Affymetrix microarray suite 4 and microarray suite 5, which use perfect-match-minus-mismatch models, and dchip and rma, which use perfect-match-only models to generate expression values. Results were validated by RT-PCR in individual animals from an independent replication of the experiment. A small number of genes was associated with escalated cocaine intake (ESC genes). Unexpectedly, of the brain regions examined [prefrontal cortex, nucleus accumbens, septum, lateral hypothalamus (LH), amygdala, and ventral tegmental area], the LH was the most transcriptionally responsive in escalation of cocaine intake. Most of the ESC genes identified are also expressed during synaptogenesis and synaptic plasticity and include genes that code for several presynaptic and postsynaptic proteins involved in neurotransmission. These results suggest that LH intrinsic circuitry undergoes a structural reorganization during escalation of cocaine use. This remodeling of LH circuitry could contribute to the chronic deficit in reward function that has been hypothesized to drive the transition to drug addiction. Results also support the value of using multiple analysis strategies to identify the most robust changes in gene expression and to compensate for the biases that affect each strategy. Experiment Overall Design: The experimental design for this study comprised three groups of rats (n = 8) with different daily access to a continuous schedule of i.v. cocaine self-administration (0.25 mg per injection): 0 h access per day (drug-naive control rats), 1 h access per day (ShA rats), or 6 h access per day (LgA rats). Experiment Overall Design: Gene expression profiling was then performed for each dissected brain region by using Affymetrix rat neurobiology arrays.

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Cocaine self-administration alters transcriptome-wide responses in the brain's reward circuitry

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