Another Component of the Pelvic Plexus That Innervates the Penis in the Rat

ObjectivesTo determine whether the small plexus located at the base of the penis, consisting of nerves arising from the major pelvic ganglion, connecting with the sensory branch of the pudendal nerve, contains postganglionic neurons innervating the erectile tissue and urethra of the penis.MethodsA total of 22 adult male Wistar rats 3-4 months of age (weight 250-350 g) were used. The features, distribution, and topography of the small plexus were determined by gross anatomy and histologic studies (Masson's trichrome and Nissl stain). Postganglionic neurons were traced with horseradish peroxidase-wheat germ agglutinin injected in the cavernosum, spongiosum corpora, and penile urethra.ResultsThe small plexus located at the base of the penis has ganglia containing cells with large nuclei. The cells were stained with the Nissl technique confirming they are neurons. The neurons were positively labeled with horseradish peroxidase-wheat germ agglutinin after the tracer was injected in the penile structures.ConclusionsIn the male rat, the small plexus located at the base of the penis contains postganglionic neurons innervating the penile structures. These neurons can contribute to the regulation of the sexual and urinary function of the genitourinary tract. Because the rat is the main laboratory animal used in urologic studies, it is important to consider, when designing experiments or discussing results, that in addition to the major pelvic ganglion, other postganglionic neurons of the penis are provided by the small plexus. The small plexus could be named the minor pelvic ganglia and considered a component of the pelvic plexus.