Sex differences in behavior and glutamic acid decarboxylase in Long Evans rats after prolonged social isolation beginning in adolescence.

Social isolation can have long-term effects on brain development and behavior and increases the risk of developing clinical conditions, including anxiety disorders. One modulator of the stress response is gamma-aminobutyric acid, an inhibitory neurotransmitter synthesized by glutamic acid decarboxylase (GAD). This study examined sex differences in behavior and GAD expression following prolonged social isolation beginning in adolescence in Long Evans rats. Males and females were equally divided into group-housed (GH) and socially isolated conditions on Postnatal Day 28 (n = 8 per group). Beginning 5 weeks later, tests were conducted for anxietylike behaviors (open-field test and elevated plus maze), social interactions (sociability test), and spatial memory (novel object location). Sex differences in behavior were observed, with GH females showing fewer anxietylike behaviors in the open-field test and elevated plus maze and spending more time with objects (sociability task) compared to GH males. Isolation had no effect on males but increased anxiety and reduced neophilic measures in females, removing sex differences. On the sociability task, all groups spent more time with novel rats compared to objects, suggesting social interest was retained after isolation. In the hippocampus, isolation reduced GAD in both sexes, and sex differences were seen (F > M). However, no group differences in behavior were observed in the hippocampal-dependent novel object location task. Our findings suggest that prolonged social isolation beginning in adolescence is anxiogenic for female Long Evans rats. Furthermore, sex and housing impact hippocampal GABA-ergic activity, which may have important implications in the treatment of anxiety disorders. (PsycInfo Database Record (c) 2024 APA, all rights reserved).