Female rats living in small cages respond to restraint stress with both adrenocortical corticosterone release and acetylcholine release in the hippocampus.

Since we found that the stress response of acetylcholine release in the hippocampus was attenuated in male rats living in a small cage, we individually housed female rats in a large (diameter=35 cm) or a small (19 cm) cylindrical cage for 4 days and examined the response to restraint stress which was applied from 12:00 h to 13:00 h. Both groups of rats showed a significant increase in the acetylcholine release in the hippocampus, as well as an increase in corticosterone release. But neither housing condition affected the expression of the 4-day estrous cycle. We surmise that there may be a sex difference in the effect of housing condition in the stress response of acetylcholine release in the hippocampus.