Orbital or medial frontal cortical lesions have different effects on tail pressure-elicited oral behaviors in rats.

Three groups of rats were tested with daily tail pressure (TP) tests until reliable and stable baseline eating, gnawing or licking was observed. One group then received bilateral aspiration of the medial frontal cortex, a second group received orbital frontal cortical lesions, and a third group received control lesions of the motor cortex. Daily TP tests were continued postoperatively. There was no disruption of TP-elicited oral behaviors after medial frontal or motro cortex lesions. In contrast, orbital frontal lesions abolished TP behaviors on the first day postoperatively, and there was a slow recovery of TP until day 5 when the elicited behaviors were about 80% of preoperative levels. The time course of recovery of TP-elicited oral behavior closely paralleled the recovery of elective eating after orbital frontal lesions, both in the group given TP and in another group given orbital lesions but not TP. These data demonstrate a marked difference between the medial and orbital divisions of the prefrontal cortex in the mediation of stress-induced oral behavior, and we discuss our data in terms of the possible role of dopamine terminals in these regions.