The lordosis posture is a sex-specific, hormone-dependant reflex displayed by the female rat in response to flank stimulation by the male rat during copulatory behavior. Because of its dependence on hormonal cues, lordosis has been widely used as an opportunity to study the mechanism of endocrine control of behavior. Although numerous studies have focused on the neural circuitry that transduces hormonal cues to the neural impulses that produce the behavior, technical limitations have prevented a detailed analysis of the information processing that occurs at individual nodes of the pathway. By applying the transneuronal tracer, pseudorabies virus, I intend to identify populations of neurons, particularly in the periaqueductal gray (PAG), which are relevant to the somatic control of lordosis. Specifically, the studies described in this proposal will address questions regarding the exact site(s) of estrogen and GABA interactions within this network.