Pudendal nerve topography in the rat spinal cord projections studied with the axonal tracer wheat germ agglutinin conjugated-horseradish peroxidase.

Abstract

The spinal cord termination of the sensory fibers of the rat pudendal nerve has been determined by using the transganglionic transport of horseradish peroxidase conjugated to wheat germ agglutinin. The gross anatomical examination of the pudendal plexus indicated the existence of dorsal and ventral branches in the sensory division of the pudendal nerve. Either branch or both were sectioned and exposed to a 1% solution of the enzyme. After an average survival period of 48 hours, the resulting reaction product was studied both at the level of the dorsal root ganglia and the spinal cord. Labeled dorsal root ganglion cells were observed between L1 and S4 (peak in S1 and L6). Evidence of transganglionic transport of the tracer was observed from L5 to S2. The ventral branch projected medially in the superficial dorsal horn, while the dorsal branch projected laterally. Our findings are consistent with a segregation of sensibilities for the ventral and dorsal branches that convey urogenital (ventral branch) and anal (dorsal branch) cutaneous sensations at the level of termination of primary afferents.