Poststimulation inhibition of the micturition reflex induced by tibial nerve stimulation in rats

The purpose of this study was to determine the effect of tibial nerve stimulation (TNS) on the micturition reflex. Experiments were conducted in 24 rats under urethane anesthesia. A catheter was inserted into the bladder via the bladder dome for saline infusion. A cuff electrode was placed around right tibial nerve for stimulation. TNS (5 Hz, 0.2 msec pulse width) at 2-4 times the threshold (T) intensity for inducing a toe movement was applied either during slow (0.08 mL/min) infusion of the bladder or for 30 min with an empty bladder. TNS had no effect on the micturition reflex when it was applied during slow bladder infusion. However, the 30-min TNS applied with an empty bladder induced poststimulation inhibition and significantly (P < 0.05) increased the bladder capacity to about 140% of prestimulation level in a 50-min period following the termination of stimulation. The bladder compliance was also significantly (P < 0.05) increased after the 30-min TNS. These results suggest that different mechanisms might exist in acute- and post-TNS inhibition of micturition reflex. The animal model developed in this study will be very useful for further investigations of the neurotransmitter mechanisms underlying tibial neuromodulation of bladder function.