Hormonal determinants during infancy of adult sexual behavior in the male rat

Abstract

Male rats were castrated at 16 hr after birth and then injected with either 10, 100 or 1000 μg of testosterone propionate (TP), or 10, 50 or 500 μg of estradiol benzoate (EB) at 96 hr. These animals exhibited almost no lordosis behavior when injected with estrogen and progesterone in adulthood, while control animals (which had been castrated only or castrated and injected with oil) exhibited lordosis identical to that seen in normal females. Following TP injections given in adulthood, the male rats which had received TP in infancy exhibited less mounting behavior than did the control animals, while those males which had received the two lower doses of EB exhibited significantly more mounting behavior. In comparison to female rats which had received the same doses of the same hormones in another experiment, the males in all treatment groups (except 500 μg EB) exhibited less lordosis behavior, but were not different in the amount of mounting and intromission behavior shown. Thus the neural mechanisms controlling lordosis are present in adult rats of either genetic sex if hormones are absent during infancy, but these mechanisms are suppressed if either TB or EB is present in infancy.