Sex-dependent effects of amygdaloid lesions on the social play of prepubertal rats

Male and female prepubertal rats, like many primate species, differ in the frequency with which they engage in social play (play-fighting); males engage in more social play than females. This sex difference in the rat has been found to be under the control of gonadal hormones acting during the neonatal period. In the present study we examined the effects of lesions of the amygdala, a prominent neuroendocrine control area, on the play-fighting of male and female prepubertal rats. Bilateral, electrolytic lesions and sham control treatments were made at 21 or 22 days of age and the animals were then observed daily in intact groups between 26 and 40 days of age. Amygdaloid lesions suppressed social play in male rats to levels that were indistinguishable from those of control females. In contrast to males, amygdaloid lesions had no effect on the social play of females. Sex differences in the anatomy and physiology of the amygdala are discussed as a possible explanation of its apparent differential influence on the social play of male and female prepubertal rats.