Influence of androgen in the neonatal period on ejaculatory and postejaculatory behavior in the rat

Abstract

The objective of the present report was to investigate the influence of androgen in the neonatal period on the development of ejaculatory and postejaculatory behavior. At birth, male rats were either castrated (neonatally castrated males), implanted with a Silastic tube of the aromatase inhibitor androsta-1,4,6-triene-3,17-dione for the first 10 days (ATD males), or left untreated (normal males). Female rats were either injected with 0.5 mg testosterone propionate (TP) on Days 1 (day of birth) and 2 (androgenized females) or left untreated (normal females). All gonadally intact animals were castrated at 60 days of age. Following TP administration, all animals were tested for ejaculatory and postejaculatory behavior under both shock and nonshock conditions. All animals were capable of showing the intromission pattern; however, the ejaculatory pattern was exhibited regularly only by those animals exposed to androgen at birth (normal males, androgenized females, and ATD males). The normal males required fewer intromissions to achieve ejaculation than the other two groups exhibiting this reflex. This result is discussed in terms of peripheral genital stimulation deficits and the differentiation of neural tissue responsible for masculine copulatory behavior. Androgenized females and ATD males displayed a refractory period, characterized by 22-kHz vocalizations, equal to or longer than that found in normal males. These results indicate that defeminization is not necessary for the display of normal ejaculatory and postejaculatory behavior.