Electrophysiological study of neural activity in penile nerve of the rat.

Electrophysiological techniques were used to examine the axonal composition and reflex activity of the penile nerve of the rat. Stimulation of either the pelvic nerve, hypogastric nerve, or sympathetic chain elicited synaptic and axonal volleys in the penile nerve. Synaptic responses were suppressed by nicotinic ganglionic blockade, indicating that they were mediated by cholinergic transmission in peripheral ganglia. Axonal volleys represented in part afferent pathways from receptors in the pelvic muscles, perineum, and anus. Stimulation of the penile or pelvic nerves increased intracavernous pressure. Stimulation of the dorsal nerve of the penis elicited central reflexes (50- to 150-ms latencies) in the penile nerve. Those reflexes were not eliminated by acute or chronic spinalization (T8) but were abolished by transection of preganglionic nerves, indicating an origin in the lumbosacral spinal cord. Thus the penile nerves are composed of a heterogenous population of afferent and efferent axons. Reflex activity elicited in these nerves by stimulation of pathways from the penis is probably involved in the initiation of penile erection.