Long-term functional study on the artificial bladder reflex arc established by abdominal reflex after spinal cord injury

Objective To establish an artificial bladder reflex arc in SD rats by abdominal reflex pathway above the horizon of spinal cord injury to reinnervate the neuropathic bladder and restore bladder function It involves a skin reflex arc (lower abdominal reflex pathway)with a modified efferent branch that passes the motor impulses to the bladder and initiate autonomic bladder detrusor contraction Methods This was achieved by intradural microanastomosis of the right T 13 ventral root to S 2 ventral root with autogenous nerve grafting,while leaving the right T 13 dorsal root intact After axonal regeneration, the"abdominal reflex spinal cord center bladder" new artificial bladder reflex pathway was established,and micturition was induced by scratching the right lower abdominal wall of the rats after spinal cord injury Long term function of the reflex arc was observed by nerveelectrophysiological experiments,bladder pressure tests and nervepharmacological experiments at 8 months postoperation Results Single stimuli(3 mA,0 3 ms)of the right T 13 dorsal root resulted in evoked potentials recorded from the right vesical plexus before and after the spinal cord was destroyed horizontally between L 5 and S 4 segmental level in all 12 SD rats The figure and amplitude of the evoked potentials were similar to those of the control Bladder contraction was initiated by trains of stimuli(3 mA,20 Hz,5 s)of the right T 13 dorsal root The bladder pressures increased to average 76% of normal compared to controls and the amplitude of bladder smooth muscle complex action potential increased to average 81% of normal compared to controls These figures were similar to those of the controls Atropine (0 05 mg/kg) or trimethaphan (5 mg/kg) depressed the bladder contractions initiated by the artificial bladder reflex arc and Norcuron( 4 mg/kg) didn't depress the bladder contractions Conclusions The somatic motor axons can regenerate through a segment of autogenous nerve into the parasympathetic endoneurial tubes of autonomic nerve The new pathway is mediated by cholinergic transmission involving both nicotinic(N 1)and muscarinic(M) receptors Using the survived somatic reflex above the horizon of spinal cord injury to reconstruct the bladder autonomic reflex arc by intradural microanastomosis of ventral root with a segment of autogenous nerve grafting is practical in the SD rat model and may have a potential of clinical application