Sex differences in body weight gains following amygdaloid lesions in rats.

Lesions of the most posterodorsal aspects of the amygdala resulted in equal weight gains (mean = 58 g) in male and female rats during a 22-day observation period. However, the absolute weight gains in the first 5 days after lesions were greater in females (+41.4 g) than in males (+18.8 g), as were the longer-term gains relative to their respective control groups. In a second study with female rats, it was found that amygdaloid lesions had little effect on the estrous cycle and that ovariectomy resulted in additional excessive weight gains in both rats with sham lesions and those with amygdaloid lesions. The weight gains produced by amygdaloid lesions and ovariectomy were additive. It is concluded that there is a sex difference in weight gains after amygdaloid lesions, but that the lesion-induced obesity is independent of estrogen levels. Similarities to lesions of the ventromedial hypothalamus are noted, and an amygdaloid-ventromedial hypothalamic pathway for the regulation of feeding behavior is proposed.