MATERNAL-BEHAVIOR IN MALE-RATS - EFFECTS OF MEDIAL PREOPTIC AREA LESIONS AND PRESENCE OF MATERNAL AGGRESSION

Male rats exhibit maternal behavior prepuberally and in adulthood, but the neural mechanisms and the ability of males to respond to hormones that stimulate maternal aggression (following arousal of maternal beh avior) in females have not been studied. In Experiment 1, males were e xposed to pups to stimulate maternal behavior (sensitization) after ei ther radiofrequency lesions of the MPOA or sham lesions with nonactiva ted electrodes that penetrated the MPOA. Nonsurgical males served as a CONTROL group. The LESION male group showed severe deficits in all co mponents of maternal behavior compared to the latter two groups that s howed no behavioral deficits. Females in the LESION group and those gi ven SHAM 1 lesions (produced by electrodes without current introduced into the MPOA) also showed severe deficits in maternal behavior compar ed to SHAM 2 females (electrode lowered to above the MPOA without curr ent) and nonsurgical CONTROL females. In Experiment 2, prolonged estra diol (E(2)), progesterone (P) treatment followed by an injection of ei ther 20 mu g or 100 mu g/kg estradiol benzoate (EB) or oil in castrate d males was effective in stimulating short-latency maternal behavior, mainly in the 100 mu g/kg EB group. Males of this group also showed a high level of maternal aggression that was inversely correlated with t heir latencies for maternal behavior. AII groups showed maternal aggre ssion when maternal behavior was established. The results indicate the MPOA mediates maternal behavior in males as it does in females; mater nal aggression in males accompanies the stimulation of maternal behavi or and may be stimulated by the same hormones. (C) 1996 Academic Press , Inc.