Nitric oxide relaxes rabbit corpus cavernosum smooth muscle via a potassium-conductive pathway

We tested the hypothesis that acetylcholine-induced relaxation in cavernosal tissue is the result of nitric oxide production that alters K+ conductance. In the organ bath, acetylcholine- and sodium nitroprusside-induced relaxation of corpus cavernosum were significantly attenuated by tetraethylammonium. Basal [K+]i in cavernosal smooth muscle cells was 102 +/- 11 mM using a K+-sensitive fluorescent dye. Acetylcholine produced a decrease in [K+]i to 74 +/- 10 (n > 4, P < 0.05). Tetraethylammonium pretreatment blunted the acetylcholine- and sodium nitroprusside-induced decrease in [K+]i by 82%, (n > 5, P < 0.001), respectively. L-NMMA blunted the acetylcholine- and sodium nitroprusside-induced fall in [K+]i by 93% and 83% (n > 4, P < 0.001), respectively. These data suggest that acetylcholine-mediated cavernosal smooth muscle cells relaxation occurs through nitric oxide release with activation of K+ conductance.