Behavioral Endocrinology of Male Rats with Periodic Sexual Contacts with Exclusive or Varied Females

Abstract

Sexual contact keys a profound series of acute and chronic changes in males that, presumably, are orchestrated by acute pulsatile release of hormones. An experimental paradigm is reported in which male rats were paired periodically with either the same or different estrous females to receive identical amounts of copulatory experiences. Results confirmed the hypothesis that exposure to an unfamiliar female would induce a different endocrine response which would be reflected in various androgensensitive systems. The "successively polygynous" males showed more sexual behavior than l'monogamous" males, and their respective females solicited the males differently, as well. Circulating levels of testosterone were higher immediately after sexual contact with an unfamiliar than with a familiar female partner. There were no differences in testosterone titers among the groups when the animals were killed at either 2 or 7 weeks after the final copulatory experiences. Yet, necropsies at 2 weeks postcopulation revealed that primary and secondary sex structures from polygynous males clearly were larger. Differences between the two experimental groups were reduced after 7 weeks of sexual rest, yet, polygynous males continued to show a different structural profile than the other groups. Conclusions were that males may experience greater activation of androgen-sensitive behavior and physiology following qualitatively different sexual contacts. [ P S E B M 1989 Voll92] he behavior, physiology, and morphology of sexually experienced males differ dramatically from

Steroidal interactions in the ageing endocrine system: absence of suppression and pathology in reproductive systems of old males from a mixed-sex socially stressful rat colony

“…Indeed, the responses by the reproductive system to the presence of females was similar to those reported for young males (Aumuller et al 1985;Taylor et al 1989;Albert étal. 1990).…”

“…Previous publi¬ cations detail our specific methods for measuring behaviour (Taylor et al 1991), physiology (Taylor et al 1986(Taylor et al , 1989, morphology (Komitowski et al 1988) and endocrinology (Taylor et al 1983(Taylor et al , 1989.…”

“…First, repeated aggressive encounters between males incited by unfamiliarity activates the HPA axis, resulting in release of glucocorticosteroids into the circulation followed by the loss of body weight, immunosuppression and hypertrophy of adrenal glands (Barnett, 1975;Raab et al 1986;Edens, 1987). Secondly, sexual contact stimulates the HPT axis and testo¬ sterone release is followed by growth of secondary sex accessory structures, increased epididymal sperm reserves and more efficient sexual behaviours (Kamel & Frankel, 1978;Taylor et al 1989). Colonies of familiar or unfamiliar males with or without females have provided opportunities to evaluate the reproduc¬ tive system of young adults during activation of neither, one or both axes (Mormede et al 1990).…”

Adrenal Steroids Uniquely Influence Sexual Motivation Behavior in Male Rats

“…Hormones were administered as 400 µg steroid/kg of body weight (bwt) [21]. Estradiol benzoate (100 µg/kg bwt) and progesterone (400 µg/kg bwt) were used to induce behavioral estrus in ovariectomized females [27]. …”