J Neural Transm (2000) 107: 767–777 Serotonin and sexual behavior in the male rabbit R. G. Paredes 1,4 , J. L. Contreras 2,3 , and A. Ågmo 1,2,3,5 1 Escuela de Psicología, Universidad Anáhuac, Mexico City, 2 Facultad de Ciencias Biológicas, Universidad Autónoma del Estado de Morelos, Cuernavaca, Morelos, México, 3 Departamento de Biología de la Reproducción, Universidad Autónoma Metropolitana – Iztapalapa, Mexico City, 4 Centro de Neurobiología, Universidad Nacional Autónoma de México, Querétaro, Qro, Mexico 5 Department of Psychology, University of Tromsø, Tromsø, Norway Received August 26, 1999; accepted November 4, 1999 Summary. Sexual behavior was evaluated in sexually experienced male rab- bits after the administration of different serotonergic drugs. The serotonin 1A receptor agonist 8-OH-DPAT, 1 mg/kg, inhibited male rabbit sexual behavior when animals were tested 15 min after subcutaneous (SC) administration of this compound. Lower doses, 0.25 and 0.5 mg/kg, were ineffective at a test 30 min after drug injection. Furthermore, 8-OH-DPAT, 0.25 mg/kg, failed to revert the inhibitory effects upon sexual behavior produced by lidocaine application to the rabbit penis. Stimulation of 5-HT 1B/2C receptors by TFMPP, at doses between 0.625 and 2.5 mg/kg, produced a drastic inhibition of sexual behavior when the drug was administered SC 30 min before behavioral obser- vation. Doses below 5 mg/kg were ineffective when given intraperitoneally 15 min before test. When the 5-HT 1D/2C receptors were stimulated by the agonist mCPP a reduced number of mounts and ejaculations was observed after the SC administration of 1.25 and 2.5 mg/kg. Similarly, the mixed 5-HT agonist/antagonist lisuride reduced the percentage of rabbits displaying mounting behavior 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 subtype activated. These results are at variance with previous observations in rats where 8-OH-DPAT and lisuride produced a drastic facilitation of masculine coital behavior. Moreover, while the inhibition of male sexual behavior in rats produced by TFMPP and mCPP is associated with a disruption of the execution of this behavior, in rabbits these compounds reduced sexual motivation. These results indicate that the effects of seroton- ergic drugs on sexual behavior are species specific. Keywords: Rabbit, serotonin, sexual behavior, penile anesthesia.