Figure 7.

Capsaicin sensitization–desensitization of bladder responses. (A,B) Control void and spontaneous NMCs. (C) Filling with capsaicin solution caused an initial voiding response of similar pressure characteristics as control. However, an increased level of tonic EUS activity particularly post-void was observed and voiding was incomplete. (D) At this time there was a marked increase in the amplitude of NMCs and they were accompanied by larger bursts of EMG activity. (E) Some 3 min after the application of capsaicin, intravesical infusion at the same rate continued for a longer period of time until almost twice the volume had been administered and intravesical pressure had increased twofold above that seen during the control void. This infusion triggered a striking increase in the level of EUS–EMG activity as bladder pressure rose above 20 mmHg, previously the pressure at which voiding occurred. However, small incomplete voiding episodes were seen to occur at the highest pressures accompanied by irregular EUS bursting. Normal voiding responses were non recoverable. (F) The subsequent NMCs resulted in synchronous low level tonic firing, as the EUS was markedly desensitized.