SEXUAL MOTIVATION PROMOTES OXYTOCIN SECRETION IN MALE RATS

The present study examines plasma oxytocin levels in relation to perfo rmance of copulatory behavior in male rats. The animals were divided i nto three groups: A) home-cage controls, B) sexually naive and C) sexu ally experienced. Following 15 min of sexual interactions with a sexua lly preceptive female, brought into estrus by sequential injections of estradiol benzoate (12.5 mu g animal(-1), -48 h) and progesterone (0. 5 mg animal(-1), -6 h), the male rats were decapitated. Trunk blood wa s collected for preparation of plasma samples, and subsequent radioimm unoassay for oxytocin. Home-cage controls, not exposed to a sexually p roceptive female, were decapitated at the same time as experimental an imals. It was found that plasma oxytocin levels were significantly ele vated in sexually naive rats following exposure to a sexually precepti ve female, and that plasma oxytocin levels were highly correlated with intensity of copulatory performance in these animals. In addition, it was also found that plasma prolactin and glucose levels were increase d, regardless of sexual experience, in comparison with home-cage contr ols. It is concluded that the emotional challenge, and the situation-s pecific demands for action, created by an encounter with a sexually pr eceptive female, are accompanied by an increased plasma concentration of oxytocin in sexually naive, but not sexually experienced, male rats . (C) 1998 Elsevier Science Inc.