Electrical and chemical control of smooth muscle activity of rabbit corpus cavernosum in vitro

Abstract

This study sought to further elucidate the regulation of cavernous smooth muscle tone and to characterize mechanisms of cavernous activation and relaxation. In isolated strips of rabbit corpus cavernosum, extracellular electrical and mechanical activity were recorded simultaneously before and after pharmacologic stimulation. Spontaneous mechanical activity was characterized by fast phasic contractions (frequency 6 to 30 min-1) associated with fluctuations of the extracellular electrical signals. Phasic activity was increased by blockade of potassium channels or by moderate activation of L-type calcium channels. Faster spikelike fluctuations occurred in the electrical activity, indicating the existence of spike discharges. All mechanical and electrical fluctuations were completely abolished by blockade of L-type calcium channels with nifedipine. Our results indicate that cavernous smooth muscle tone is regulated by both phasic and tonic activation mechanisms caused by the opening of L-type calcium channels and calcium influx through chemically controlled calcium influx/release.