Preoptic area and substantia nigra interact in the control of maternal behavior in the rat.

This study provides evidence that the preoptic region and the substantia nigra interact in the control of maternal behavior. In the first experiment, large electrolytic lesions of the substantia nigra were found to severely disrupt maternal behavior and cause stereotyped motor activity in postpartum lactating rats. In order to test the hypothesis that the preoptic region and the substantia nigra interact in the control of maternal behavior, a second experiment employed an asymmetrical lesion design. Postpartum lactating rats that received a unilateral knife cut severing the lateral connections of the medial preoptic area and a contralateral lesion of the substantia nigra showed larger deficits in maternal behavior than either sham females or females that received a unilateral preoptic knife cut paired with an ipsilateral substantia nigra lesion. Measurements of body weights, body temperatures, and stereotyped behavior indicated that the differences in maternal behavior between the ipsilateral and contralateral groups could not be explained on the basis of nonspecific effects.