Facilitation of sexual behaviors in the male rat associated with intra-VTA injections of opiates.

Male rats were tested for sexual behaviors after bilateral injections of morphine sulfate or dynorphin1-13 into the ventral tegmental area. Both morphine and dynorphin1-13 increased, in a dose-orderly manner, the number of males that mounted, and the display of female-directed behavior. Repeated administration of morphine, but not dynorphin1-13, into the region of the ventral tegmental area increased dopamine (DA) metabolism in the nucleus accumbens, a terminal field of the mesolimbic DA system. These results suggest that activation of elements within the region of the VTA activated by mu and kappa selective agonists are able to facilitate some aspects of sexual behavior, but that only morphine appears to activate dopaminergic elements within the VTA.