Divergent Population-Specific Effects of Chronic Ethanol Exposure on Excitability and Inhibitory Transmission in Male and Female Rat Central Amygdala.

The central nucleus of the amygdala (CeA) is implicated in alcohol use disorder (AUD) and AUD-associated plasticity. The CeA is a primarily GABAergic nucleus that is subdivided into lateral and medial compartments with genetically diverse subpopulations. GABA A receptors are heteromeric pentamers with subunits conferring distinct physiological characteristics. GABA A receptor signaling in the CeA has been implicated in ethanol-associated plasticity, however population-specific changes in inhibitory signaling and subunit expression remain unclear. Here, we combined electrophysiology with single cell gene expression analysis of population markers and GABA A receptor subunits to examine population-specific changes in inhibitory control in male and female rats following chronic ethanol exposure. We found that chronic ethanol exposure and withdrawal produced global changes in GABA A receptor subunit expression at the transcript and protein levels, increased excitability in female CeA neurons, and increased inhibitory synaptic transmission in male CeA neurons. When we examined CeA neurons at the single-cell level we found heterogenous populations, as previously reported. We observed ethanol-induced increases in excitability only in somatostatin neurons in the CeA of females, decreases in excitability only in the PKC δ population in males and observed ethanol-induced increases in inhibitory transmission in male PKC δ- and calbindin 2-expressing CeA neurons. There were no population-specific differences in GABA A receptor subunits in males, but reduced GabrA5 expression in female somatostatin neurons. Collectively, these findings suggest that defined CeA populations display differential ethanol sensitivity in males and females, which may play a role in sex differences in vulnerability to AUD or expression of AUD pathology. Significance Statement The central amygdala (CeA) is involved in ethanol's effects in the brain, however the population-specific changes in CeA activity remain unclear. We used recordings of CeA neuronal activity and single cell gene expression to examine population-specific changes in inhibitory control in male and female rats following chronic ethanol exposure and found sex- and population-specific effects of chronic ethanol exposure and withdrawal. Specifically, female CeA neurons displayed increased excitability in the somatostatin CeA population, while male CeA neurons displayed increased inhibitory control in both PKC δ and calbindin populations and decreased excitability in the PKC δ population. These findings identify CeA populations that display differential sensitivity to ethanol exposure, which may contribute to sex differences in vulnerability to alcohol use disorder.