EFFECT OF CASTRATION AND GONADAL-HORMONES ON INSULIN-INDUCED DRINKING

Female Wistar rats in any of the estrual phases have been shown to dri nk significantly more water than males (p < 0.05), after a single IP i nsulin injection (5 U/kg b.wt.). Sexual differences in insulin-induced drinking persisted after castration when it was made in adult rats (4 .6 +/- 1.2 ml/2 h, males = 8; vs. 13.0 +/- 3.1 ml/2 h, females = 8; p < 0.05). On the other hand, when animals were castrated before puberty or when newborn, sexual differences in insulin-induced drinking disap peared. Hence, insulin-induced drinking seems to be a sex-dependent ph enomenon that differentiates just before or during puberty since it is abolished by castration prior to sexual maturation. Sex hormone admin istration in male and female rats castrated at different ages showed a variety of actions on insulin-induced drinking. A pattern emerged sho wing that androgenized (testosterone treated) rats drank usually less in response to insulin than estrogen-treated rats (independent of thei r genetic sex). According to the above results, we can conclude that i nsulin-induced drinking is a phenomenon sensible to gonadal hormones, both by conditioning the differentiation of some physiological structu re or mechanisms that underlay drinking behavior in that paradigm and by a direct action on these or other related mechanisms. (C) 1998 Else vier Science Inc.