Effects of medial preoptic-anterior hypothalamic lesions on mating behavior of male cats

Abstract

Bilateral electrolytic or radiofrequency lesions causing extensive damage to the medial preoptic-anterior hypothalamic (MP-AH) area immediately and permanently abolished or markedly impaired copulatory behavior in 11 adult, sexually experienced male cats. Nine other male cats sustaining unilateral MP-AH lesions, bilateral lesions outside the critical MP-AH area, or smaller of MP-AH lesions, exhibited essentially normal copulatory behavior within 1–2 weeks after surgery. Five additional male cats with lesions more closely resembling those of subjects showing permanent impairment exhibited an initial impairment followed by recovery of virtually normal mating activity after a period ranging from 15 to 35 days after surgery. The location and size of effective MP-AH lesions, as well as the type of behavioral changes, including elimination of mounting with pelvic thrusting, closely paralleled findings previously reported on the effects of MP-AH lesions in male rats. Treatment with testosterone propionate did not restore mating activity. Examination of testicular tissue from subjects showing abolishment or impairment of copulatory behavior revealed normal histological structure. The results reveal that although the MP-AH area may be a focal point for the action of gonadal androgen in maintaining male sexual behavior, this forebrain area has a critical role in the mediation of male sexual behavior apart from its presumed function as androgen target tissue. This concept is based on the observation of immediate and permanent loss of copulatory behavior following large MP-AH lesions, compared with the more gradual reduction of sexual activity that would be expected from a type of functional castration resulting merely from removal of androgen target tissue.