The Journal of comparative neurology
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Comparative Study
The organization of pudendal motoneurons and primary afferent projections in the spinal cord of the rhesus monkey revealed by horseradish peroxidase.
The horseradish peroxidase tracing technique was utilized to study the distribution of motoneurons and primary afferent neurons contributing fibers to the pudendal nerve in the monkey. Application of horseradish peroxidase to the central cut end of the pudendal nerve labeled motoneurons in the ipsilateral spinal cord primarily in the S1 and L7 segments. In transverse sections these neurons were distributed within an oval area (Onuf's nucleus) with an average dimension of 360 X 290 micron, located at the base of the ventral horn, medial to the lateral motor nuclei. ⋯ The majority of labeled lateral afferent axons ended slightly dorsal to the sacral parasympathetic nucleus. A comparison of the present findings with previous descriptions of the sacral visceral pathways shows a considerable overlap in certain areas of the spinal cord of pudendal and pelvic nerve afferent and efferent systems. This close anatomic relationship is consistent with the physiological observation that somatovisceral integration in the lumbosacral spinal cord is essential for the normal regulation of micturition, defecation, and sexual function.