Effects of medial preoptic lesions on placentophagia and on the onset of maternal behavior in the rat

Lesions of the medial preoptic area (MPO) were produced through permanently indwelling electrodes 24 hr prior to parturition in pregnant rats, or 24 hr prior to donor-placenta presentation in virgin rats determined in a pretest to be placentophages. The lesions had no disruptive effect on placentophagia in the virgin females. However, MPO lesions did delay the onset of placentophagia, pup-retrieval, and nest-building in some parturient rats. In others, lesions produced an impairment (in latency and quality) only of nest-building. None showed any impairment of pup-licking, or in the clear tendency to leave excreted waste away from the gathered pups. These results suggest the possibility of at least semi-independent mechanisms for the various components of maternal behavior.