Prolonged inhibitory effect of repeated period tibial nerve stimulation on the micturition reflex in the rat

Background : The aims of this study was determine if stimulation of tibial nerve afferents could induce a prolonged modulation of the micturition reflex in the rats.  Methods: Fifteen female Sprague Dawley rats (250-350 g) were fully decorticated and paralysed for the study. Tibial nerve stimulation (TNS) was  delivered by inserting two pairs of needle electrodes close to the nerves at the level of the medial malleolus. Constant flow cystometries (0.07 ml/min) at about 10 min interval were performed and the micturition threshold volume (MTV) was recorded and used as the dependent variable. After 4 - 5 stable control recordings, the tibial nerves of both sides were stimulated continuously for 5 min at 10 Hz, 3 times threshold for α-motor axons. Six times of same stimulation were applied repeatedly with an interval of 5 min between the stimulations. The mean MTV was compiled from several cystometries in each half hour before the TNS and during, after 6 periods TNS. Results: During the experiment, all the animals survived in a good condition with reasonably stable micturition reflexes, a significant increase in MTV was revealed after TNS. The best effect (mean 178%) occurred during the first 30 min after 6 periods of stimulation. This clear threshold increase remained for at least 5 h. Conclusions: A prolonged increase in MTV was demonstrated by a short periods of TNS repeatedly. This post stimulation modulatory effects of micturition reflex would provide a theoretical explanation for the clinical beneficial effect of TNS in patients with overactive bladder (OAB).