Effects of voluntary ethanol consumption on emotional state and stress responsiveness in socially isolated rats.

Social isolation of rats immediately after weaning is thought to represent an animal model of
anxiety-like disorders. This mildly stressful condition reduces the cerebrocortical and plasma
concentrations of 3?-hydroxy-5?-pregnan-20-one (3?,5?-TH PROG) as well as increases the
sensitivity of rats to the effects of acute ethanol administration on the concentrations of this
neuroactive steroid. We further investigated the effects of voluntary consumption of ethanol at
concentrations increasing from 2.5 to 10% over 4 weeks of isolation. Isolated rats showed a
reduced ethanol preference compared with group-housed animals. Ethanol consumption did not
affect the isolation-induced down-regulation of BDNF or Arc, but it attenuated the increase in
the cerebrocortical concentration of 3?,5?-TH PROG induced by foot-shock stress in both
isolated and group-housed animals as well as increased the percentage of number of entries
made by socially isolated rats into the open arms in the elevated plus-maze test. Ethanol
consumption did not affect expression of the ?4 subunit of the GABAA receptor in the
hippocampus of group-housed or isolated rats, whereas it up-regulated the ? subunit throughout
the hippocampus under both conditions. The results suggest that low consumption of ethanol
may ameliorate some negative effects of social isolation on stress sensitivity and behavior.