Abstract
The medial preoptic area (MPOA) is an integral site for male sexual behavior. Dopamine is
released in the MPOA before and during copulation and facilitates male rat sexual behavior.
Repeated sexual experience and noncopulatory exposures to an estrous female facilitate
subsequent copulation. However, the neurobiological mechanisms that mediate such enhancement
remain unclear. Here, we examined the role of dopamine D1 receptors in the MPOA in
experience-induced enhancement of male sexual behavior in rats. In Experiment 1,
microinjections of the D1 antagonist SCH-23390 into the MPOA before each of 7 daily 30-min
noncopulatory exposures to a receptive female impaired copulation on a drug-free test on day 8,
compared to vehicle-treated female-exposed animals. Copulatory performance in drug-treated
animals was similar to vehicle-treated males that had not been pre-exposed to females. This effect
was site specific. There were no group differences in locomotor activity in an open field on the
copulation test day. In Experiment 2, a separate cohort of animals was used to examine
phosphorylation of dopamine-and cAMP-regulated phosphoprotein (DARPP-32) in the MPOA of
animals with acute and/or chronic sexual experience. DARPP-32 is a downstream marker of D1
receptor signaling and substrate of cAMP-dependent protein kinase (PKA). Western immunoblot
analysis revealed that p-DARPP-32 expression was greatest in the MPOA of males that received
both acute and chronic sexual experience, compared to all other mated conditions and naïve
controls. These data suggest that D1 receptors in the MPOA contribute to experience-induced
enhancement of male sexual behavior, perhaps through a PKA regulated mechanism.