Urethral Sphincteric Responses to Stimulation of the Sacral Nerves in the Human Female

Stimulation of the human sacral nerves evokes, at higher voltages, a urethral relaxation which may be independent of bladder contraction. It persists after nerve section when the distal cut end is stimulated, but does not occur on stimulating the proximal end. It is presumed to represent parasympathetic efferent inhibition, and is the pathophysiological basis for the ‘unstable urethra’ syndrome.