Comparison of neural targets for neuromodulation of bladder micturition reflex in the rat

Abstract

Spinal nerve (SN) stimulation inhibits the bladder rhythmic contraction (BRC) in anesthetized rats. This preparation was used to study the effects of electrical stimulation of the tibial nerve (TN) and the dorsal nerve of the clitoris (DNC) on BRC. Stimulation of the TN and DNC for 10 min produced a frequency- and intensity-dependent attenuation of the frequency of bladder contractions. As observed with the SN, 10-Hz stimulation of either TN or DNC produced the greatest degree of inhibition, with lower or higher frequencies being either less efficacious or inactive. In contrast to the prolonged inhibition produced by SN stimulation, both TN and DNC stimulation produced "short" lasting inhibition of bladder contractions and the maximal inhibition occurred during stimulation. TN stimulation was effective over only a narrow range of current intensities [3-4 × motor threshold current for inducing a toe twitch (T(mot))] and only at a frequency of 10 Hz. Stimulation of TN at 10 Hz, 3 × T(mot) inhibited BRC to 23% of control. Ten-hertz DNC stimulation at 2 × T(EAS), the threshold current for evoking a reflex anal sphincter contraction, decreased the frequency of contractions to 4% of control. Although compared with the respective threshold current the BRC response was more sensitive to DNC compared with TN stimulation, the absolute current required to reduce BRC using DNC stimulation appeared to be higher. Comparing the effects of TN and DNC stimulation to our previous results with SN stimulation, SN stimulation produces the largest duration and efficacy of bladder inhibition.