Visceral afferent and different fibers in sacral ventral roots in cats

Abstract

(1) It was demonstrated by electrophysiological techniques that a few afferent fibers of pelvic nerve origin enter the spinal cord through sacral ventral roots in the cat. These fibers were activated by receptors in the bladder and rectal walls. Somatic afferent fibers in the sacral ventral roots were also identified. (2) Fibers of pelvic nerve origin in sacral ventral roots and conducting at velocities from approximately 15 to 50 m/sec represent only a very small proportion of the total population of pelvic nerve fibers. The conduction velocities were similar to those of dorsal root fibers derived from the pelvic nerve and it is suggested that these fast conducting fibers are the afferent fibers now demonstrated, and not parasympathetic preganglionic axons. (3) Previous conclusions derived from single unit studies regarding the distribution of conduction velocities in parasympathetic preganglionic axons were fully confirmed by a careful analysis of ventral root volleys.