Horseradish peroxidase tracing of visceral efferent and primary afferent pathways in the cat's sacral spinal cord using benzidine processing.

Sacral afferent and preganglionic efferent neurons were labelled by applying horseradish peroxidase (HRP) to the central end of the transected pelvic nerve. Preganglionic cells were evident as a narrow band of cells extending from the intermediolateral region dorsomedially beneath the dorsal horn. Their dendrites were located primarily within the nucleus but also projected into the dorsolateral funiculus, along the lateral edge of the dorsal horn and to dorsal commissure. Labelled primary afferent axons and/or terminals were detected in Lissauer's tract and in the marginal zone of the dorsal horn extending from the apex ventrally along its lateral edge into the dorsal region of the autonomic nucleus. These observations suggest that sacral preganglionic neurons may receive monosynaptic connections from pelvic nerve afferents.