Synchronized Electrical Stimulation of the Sympathetic and Parasympathetic Innervation of the Bladder: Facilitation of the Initiation of Micturition in the Dog

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Abstract
To improve the quality of bladder contractions induced by parasympathetic stimulation and to facilitate the initiation of voiding, we investigated the effect of sympathetic stimulation on the parasympathetic innervation of the bladder in 12 dogs. For the sympathetic system, the lumbar sympathetic trunks were electrically stimulated; for the parasympathetic system, either the pelvic nerve or the ventral root of S2 was stimulated. With voltages at or just above the threshold for achieving a measurable effect on bladder pressure, stimulation of the sympathetic system or the pelvic nerve alone did not lead to voiding, and sacral root stimulation alone elicited voiding in only 7.4 per cent of stimulations. However, when the same stimulus parameters were used for synchronous stimulation, the voiding process was facilitated when sympathetic stimulation was begun five to 10 seconds before parasympathetic stimulation. When the pelvic nerve was used, voiding resulted in 77.7 per cent of stimulations and the bladder was emptied by a mean of 68.7 per cent; with S2 ventral root stimulation, voiding resulted in 83.3 per cent of stimulations and the bladder was emptied by 59.7 per cent. The facilitory effect of sympathetic stimulation was not abolished when the sympathetic trunks were cut centrally to the point of stimualtion, but was absent when the hypogastric nerves were transected. We feel that sympathetic stimulation modulate the parasympathetic innervation of the bladder.