Effects of Chronic Social Stress on the transcriptome of BA-NAc neurons

Reduced reward interest/learning and reward-to-effort valuation are distinct, common symptoms in neuropsychiatric disorders for which chronic stress is a major aetiological factor. Pyramidal glutamate neurons in the basal amygdala (BA) project to various brain regions including nucleus accumbens (NAc). The BA-NAc neural pathway is activated by reward and aversion, with many neurons being monovalent. In adult male mice, chronic social stress (CSS) led to both reduced discriminative reward learning (DRL) associated with decreased BA-NAc Ca2+ activity, and reduced sucrose reward-to-effort valuation (REV) associated, in contrast, with increased BA-NAc Ca2+ activity. Chronic tetanus toxin inhibition of BA-NAc neurons replicated the CSS-DRL effect whilst causing only a mild REV reduction, whilst chronic DREADDs activation of BA-NAc neurons replicated the CSS effect on REV without affecting DRL. This study provides novel evidence that chronic stress disruption of reward processing involves the BA-NAc neural pathway; the bi-directional effects implicate activity changes in BA-NAc reward (learning) and aversion (effort) neurons, with the net overall direction of stress-induced change in activity dependent on on-going stimulus processing and behaviour. Assessment of the effects of chronic social stress on the transcriptome of BA-NAc "reward-sensitive" glutamatergic neurons when compared to BA-Nac glutamatergic neurons from control non-stressed animals.