8-OH-DPAT INTERACTS WITH SEXUAL EXPERIENCE AND TESTOSTERONE TO AFFECTEJACULATORY RESPONSE IN RATS

Studies investigating the effect of 8-OH-DPAT (DPAT) on male sexual re sponse have typically used subjects having variable sexual experience and levels of testosterone, factors known to independently influence m ale sexual behavior. This experiment examined the role of these two va riables in the mediation of DPAT effects on sexual behavior. One hundr ed and six castrated males, half of whom received sexual experience, w ere tested with an effective dose of 8-OH-DPAT (0.1 mg/kg) or saline. In addition, males were tested under one of three regimens of testoste rone. Results indicated that DPAT and testosterone exerted independent effects on ejaculatory measures, and along with sexual experience, sh owed interactive effects as well. When testosterone (T) levels were su bstantially below normal, DPAT showed no effect. When T reached thresh old levels, the DPAT effect was limited to sexually experienced males. At high T levels, both experienced and naive males exhibited strong e ffects from DPAT. In contrast with ejaculatory measures, mounting and intromitting behaviors were relatively unaffected by DPAT. These resul ts emphasize the importance of specifying both the animal's sexual his tory and its testosterone profile in studies investigating pharmacolog ical effects on sexual response. (C) 1998 Elsevier Science Inc.