This study shows for the first time the presence of interstitial cells of Cajal (ICC) and their possible role in the initiation of spontaneous excitation in the corporal tissue of the guinea-pig penis. ICC, which were identified by their c-kit immunoreactivity, were abundantly distributed in the corporal smooth muscle meshwork. Spontaneous increases in the intracellular calcium concentration ([Ca2+]i; calcium transients) were visualized in preparations loaded with the fluorescent dye fura-2. Ca transients originated from the boundary of muscle bundles and then spread throughout the meshwork (Ca waves). Ca waves were strongly suppressed by either CPA (10 μM), ryanodine (50 μM) or 2-APB (10 μM), and their synchronicity was disrupted by 18β-GA (30 μM). These results suggest that ICC in the corporal tissue may have a role as pacemakers to drive the bulk of smooth muscles, and that intracellular Ca2+ stores and gap junctions are critical for the generation of spontaneous excitation.
British Journal of Pharmacology (2004) 141, 199–204. doi:10.1038/sj.bjp.0705622