Higher CNS control of penile responses in rats: the effect of hypothalamic stimulation

The effect of electrical stimulation of the medial preoptic area (MPOA) of the hypothalamus on penile responses in rats was investigated. No females were present and penile responses were observed through the use of an inclined mirror. MPOA stimulation was found to elicit two types of penile responses: penile movement within the sheath and protrusion of the penis outside the penile sheath. While these responses also occurred spontaneously during the nonstimulation control sessions, they occurred in significantly higher frequencies following MPOA stimulation. The results also produced an unexpected finding. While studies on the effect of hypothalamic stimulation on copulation show stimulation-bound effects, MPOA stimulation in the absence of a receptive female consistently triggered penile responses as a poststimulation effect.