Avoidance behavior and plasma prolactin levels in lergotrile mesylate treated rats

We have previously shown that psychological factors play a major role in control of prolactin (PRL) secretion, and that PRL increases during shock-motivated avoidance conditioning. In the present studies, we examined whether we could attenuate acquisition performance by suppressing the PRL increase during avoidance testing. Rats were tested daily in a shuttle box. They were presented with a light stimulation followed by an electric footshock. During each trial, the rats were given the opportunity to escape the footshock by moving to a safe side of the box. Movement to the appropriate location after the warning signal (light) begins, but before the onset of the footshock, constitutes a conditioned avoidance response (CAR). Experimental rats were fitted with an intraperitoneal osmotic minipump which delivered lergotrile mesylate (LM), 0.69 mg/kg/day. Blood samples were collected from an indwelling cannula and analyzed by radioimmunoassay. Administration of LM blocked the PRL increase that occurred during early avoidance testing, but did not alter the acquisition of a CAR. These data do not support the idea that PRL acts to facilitate acquisition of avoidance behavior.