ELECTRICAL AND CHEMICAL CONTROL OF SMOOTH-MUSCLE ACTIVITY OF RABBIT CORPUS CAVERNOSUM IN-VITRO

Objectives. This study sought to further elucidate the regulation of c avernous smooth muscle tone and to characterize mechanisms of cavernou s activation and relaxation. Methods. In isolated strips of rabbit cor pus cavernosum, extracellular electrical and mechanical activity were recorded simultaneously before and after pharmacologic stimulation. Re sults. Spontaneous mechanical activity was characterized by fast phasi c contractions (frequency 6 to 30 min(-1)) associated with fluctuation s of the extracellular electrical signals. Phasic activity was increas ed by blockade of potassium channels or by moderate activation of L-ty pe calcium channels. Faster spikelike fluctuations occurred in the ele ctrical activity, indicating the existence of spike discharges. All me chanical and electrical fluctuations were completely abolished by bloc kade of L-type calcium channels with nifedipine. Conclusions. Our resu lts indicate that cavernous smooth muscle tone is regulated by both ph asic and tonic activation mechanisms caused by the opening of L-type c alcium channels and calcium influx through chemically controlled calci um influx/release.