Socio-sexual behavior in male rats after lesions of the dorsolateral tegmentum

The medial preoptic area of the anterior hypothalamus (MPOA/AH) and the dorsolateral tegmentum (DLT) play an important role in the control of sexual behavior. Unilateral lesions of the MPOA/AH (medial preoptic area of the anterior hypothalamus) combined with unilateral lesions of the contralateral DLT result in deficits in male sexual behavior, while bilateral electrolytic lesions of the DLT have similar effects. In the present study, coital and socio-sexual interactions were recorded before and after bilateral electrolytic DLT lesions. Coital behavior was monitored for 15 weeks after surgery and socio-sexual interactions one 1 and 3 weeks after lesion. DLT-lesioned animals showed reduced copulatory behavior throughout the 15 weeks postlesion. This inhibition was associated with changes in exploratory (sniffing), precopulatory (pursuit and genital exploration), and postcopulatory behaviors (self-grooming). No differences were found in the weights of the testicles, prostate and seminal vesicles. These results indicate that lesions of the DLT produced permanent deficits in sexual behavior associated with a generalized modification of sociosexual behavior. These deficits indicate reduced sexual motivation possibly due to the disruption of the output pathway from the MPOA/AH (medial preoptic area of the anterior hypothalamus) to the DLT. (C) 1998 Elsevier Science Inc.