NURSING POSTURE IS ELICITED RAPIDLY IN MATERNALLY NAIVE, HALOPERIDOL-TREATED FEMALE AND MALE-RATS IN RESPONSE TO VENTRAL TRUNK STIMULATION FROM ACTIVE PUPS

Maternal responsiveness in rats can be induced in virgin females and males, without hormonal priming, following several days of cohabitation with pups. Because antagonism of dopamine (DA) facilitates nursing behavior in lactating rats, the response of nonlactating, maternally naive rats to effective stimulation of the ventral trunk (ventrum) from pups following similar treatment was investigated. Lactating dams, virgin females and males, both intact and gonadectomized, were treated with a catalepsy-inducing dose of haloperidol (5 mg/kg), a DA receptor antagonist, and tested with hungry pups 1 hr later. Subjects were placed over 8 pups and postures assessed every 3 min for 30 min. The nursing posture occurred in most subjects. Lactating and nonlactating females were similar in occurrence of the nursing crouch, though the intensity was somewhat higher in the former; females scored higher than males in terms of likelihood and intensity of crouching; and there was no effect of gonadectomy. The nursing posture was not elicited in intact virgin females if the stimulus pups were anesthetized or if the subjects were treated with saline instead of haloperidol. There were no sex differences in onset or intensity of catalepsy in response to the dose of haloperidol used. These results suggest that the nursing posture occurs reflexively, is not directly dependent upon ovarian hormones, and is diminished by the effects of androgens, prior and current. © 1991.