Behavioral and adrenal responses and meal expectancy in rats with fornix transection.

The behavioral and corticosterone responses of control rats and rats with fornix transections were examined during eating sessions and when consummatory behavior was blocked but cues controlling the behavior were maintained. Rats with fornix transection exhibited increased frequencies of eating, trips away from the food cup, and exploration, but decreased durations of these behaviors, and differential organization of behavior during eating and blocked eating sessions. Control rats exhibited increased corticosterone levels to blocked eating; fornix transected rats did not. The groups did not differ on basal corticosterone levels or hormonal responses to deprivation, and neither group exhibited conditioned hormonal responses to repeated sampling. The results indicate that control rats, but not rats with fornix transection, respond to the violation of an expectation with increased corticosterone levels.