[An electrophysiological study on the artificial somato-autonomic pathway for inducing voiding]

To investigate the possibility of regeneration of somatic motor nerve to replace splanchnic nerve and the electrophysiologic characters of the regenerated nerve.

An artificial somato-autonomic reflex pathway was established by intradural microanastomosis of L(4) ventral root (VR) to L(6)VR at the left side in 12 male Wistar rats. Then the L(4)VR proximal to the anastomosis was stimulated by silver electrode and the evoked potentials were recorded on the distal end to the anastomosis, pelvic nerve and postganlionic fibers of the major pelvic ganglia (MPG). Cystometrography was used to record the intravesical pressure. Hexamethonium, a cholinergic ganglion blocker, was given directly on the pelvic ganglion so as to observe the change of the intravesical pressure evoked by stimulation of the nerves. Another 12 rats were used as controls.

(1) In the experimental group, stimulation of the L(4)VR proximal end to the anastomosis evoked potentials on the distal end, the pelvic nerve, and the postganglionic fibers of the MPG, and induced bladder contraction. Stimulation of the contralateral sciatic nerve failed to evoke change of intravesical pressure. In the control group stimulation of the L(4)VR or sciatic nerve failed to evoke potentials on the postganglionic fibers of pelvic nerve and change of intravesical pressure. (2) Stimulation of the ipsilateral sciatic nerve led to an increase of intravesical pressure. (3) After the use of hexamethonium stimulation of the ipsilateral sciatic nerve and proximal end of L(4)-L(6) anastomosis failed to evoke change of intravesical pressure. (4) The conduction velocity of the regenerated motor axons was 33.3 m/s +/- 6.9m/s, significantly higher than that of the control group (11.6 m/s +/- 1.6 m/s).

Somatic motor axons can regenerate to the MPG and reinnervate the bladder and the impulses from the somatic motor neurons can initiate voiding.