Studies on vesicourethral reflexes. II. Urethral sphincteric responses to spinal cord stimulation

A bipartite bladder model was developed with and without complete muscular separation in order to isolate and analyze separately sphincteric and detrusor responses. Spinal cord stimulation of the sacral micturition center evoked responses in the detrusor compartment as well as in the urethral sphincteric compartment. The micturition center was easily definable in the spinal cord at a variable point lying in the segment L51/2 to L6 vertebral levels. It was not possible to isolate a separate detrusor center from a sphincteric center. They did overlap-with the sphincteric center extending both above and below the detrusor center. Parameters of stimulation were tested and it was noted that 1 to 3 v, frequency of 10 to 15 cps, and duration of 1 msec gave the optimal responses. Complte muscular separation did not alter sphincteric response to spinal cord stimulation. Nerve-mediated impulses resulted in rise in detrusor pressure and a simultaneous rise in urethral pressure that interfered with proper voiding and hindered bladder emptying. This problem remains to be solved before central spinal cord stimulation for the purpose of controlled bladder evacuation becomes fully effective.