LESIONS OF THE MEDIAL AMYGDALA PRODUCE SEVERE IMPAIRMENT OF COPULATORY-BEHAVIOR IN SEXUALLY INEXPERIENCED MALE-RATS

The effects of amygdaloid lesions on masculine copulatory behavior were examined in male rats. Sexually inexperienced male rats were castrated and subjected to bilateral lesions in one of the following areas: the medial amygdala, the cortical amygdala, or the basolateral amygdala. Three weeks later, all rats received implantation of silastic capsules containing testosterone. Then, four observations of copulatory behavior were carried out every 5 days following the implantation of testosterone. Rats with medial amygdala lesions showed a severe deficit of copulatory behavior, whereas rats with basolateral amygdala lesions showed no change in the performance of copulation. As for rats with cortical amygdala lesions, although their copulatory behavior was impaired, the effect was confined to a deficit in intromission and ejaculation responses. These findings suggest that the medial amygdala plays a critical role in regulating masculine sexual behavior in the rat.