Figure 6.

Effect of nicotinic receptor blockade on micturition. (A) Topical vecuronium bromide (a competitive antagonist of neuromuscular transmission) applied to the EUS (10 μl; 2 μg/μl; (ii), caused a decrease in EUS–EMG activity within 2 min but voiding still occurred, albeit at a lower pressure [compared to control; (i)]. In particular, during the void, fewer and lower amplitude EUS-EMG bursts were observed. (iii) A second application of vecuronium completely abolished EUS–EMG activity and further infusion caused passive leakage of urine. In order to test the EUS activity, the distal urethra was clamped to allow bladder pressure to increase. No EUS activity was evoked. This block was maintained for the following 30 min without sign of recovery. (B) Application of the ganglion blocker hexamethonium [330μM; (ii)] to the perfusate blocked the cardiovascular responses to peripheral chemoreflex activation indicating that the sympathetic and parasympathetic outflows were blocked. There was an initial decrease in the voiding pressure, although the characteristic pressure trajectory and EUS bursting activity remained. (iii) After a further 2 min, NMCs became larger (arrowed) in amplitude, with associated EUS activity to maintain continence. Voiding was present, but altered, with low voiding pressure and high baseline intravesical pressures.