Serotonin and sexual behavior in the male rabbit

Sexual behavior was evaluated in sexually experienced male rabbits after th e administration of different serotonergic drugs. The serotonin(1A) recepto r agonist 8-OH-DPAT, 1 mg/kg, inhibited male rabbit sexual behavior when an imals were tested 15 min after subcutaneous (SC) administration of this com pound. Lower doses, 0.25 and 0.5 mg/kg, were ineffective at a test 30 min a fter drug injection. Furthermore, 8-OH-DPAT, 0.25 mg/kg, failed to revert t he inhibitory effects upon sexual behavior produced by lidocaine applicatio n to the rabbit penis. Stimulation of 5-HT1B/2C receptors by TFMPP, at dose s between 0.625 and 2.5 mg/kg, produced a drastic inhibition of sexual beha vior when the drug was administered SC 30 min before behavioral observation . Doses below 5 mg/kg were ineffective when given intraperitoneally 15 min before test. When the 5-HT1D/2C receptors were stimulated by the agonist mC PP a reduced number of mounts and ejaculations was observed after the SC ad ministration of 1.25 and 2.5 mg/kg. Similarly, the mixed 5-HT agonist/antag onist lisuride reduced the percentage of rabbits displaying mounting behavi or at doses of 0.25 and 0.5 mg/kg SC. All compounds tested produced a clear inhibition of male rabbit sexual behavior independently of the receptor su btype activated. These results are at variance with previous observations i n rats where 8-OH-DPAT and lisuride produced a drastic facilitation of masc uline coital behavior. Moreover, while the inhibition of male sexual behavi or in rats produced by TFMPP and mCPP is associated with a disruption of th e execution of this behavior, in rabbits these compounds reduced sexual mot ivation. These results indicate that the effects of serotonergic drugs on s exual behavior are species specific.