Preganglionic C-fibres: a major component of the sacral autonomic outflow to the colon of the cat.

The sacral preganglionic pathways to the colon and urinary bladder of the cat were studied with electrophysiological techniques. Peak conduction velocities in preganglionic fibres to the colon ranged from 0.5 to 1.4 m/sec, whereas maximum velocities in the bladder pathway were between 8 to 10 m/sec. Thresholds for electrical stimulation of preganglionic axons to the colon were 7 to 10 times higher than thresholds for bladder efferents. It is concluded that the sacral parasympathetic inputs to the colon and bladder are composed, respectively, of non-myelinated and myelinated fibres.