AN IN-VITRO STUDY OF NONADRENERGIC-NONCHOLINERGIC ACTIVITY ON THE CAVERNOUS TISSUE OF MOUSE

The relaxant effects of electrical field stimulation (EFS) and exogeno usly applied acetylcholine (ACh) or acidified NaNO2 (a-NaNO2) were inv estigated in the isolated mouse corpus cavernosum precontracted with p henylephrine hydrochloride (PE). Tetrodotoxin (TTX) blocked the relaxa nt effects of EFS completely, whereas it had no effect on the response s to ACh or a-NaNO2. Guanethidine and indomethacin failed to affect th e electrically or ACh-induced relaxations. Atropine completely blocked the effect of ACh; however, it caused a slight reduction in the relax ation evoked by EFS. N-G-Nitro-L-arginine (L-NOARG) reduced the effect s of EFS and ACh significantly, but it was ineffective on the relaxati ons induced by a-NaNO2. The inhibitory action of L-NOARG was partly re stored by L-arginine, but not by D-arginine. Methylene blue (MB) and h ydroxocobalamin (HC) exhibited significant inhibition on the relaxatio ns evoked by EFS, ACh and a-NaNO2. Hydroquinone (HQ) reduced relaxatio n due to a-NaNO2, but did not affect that of EFS and ACh. Our findings suggest that EFS-induced relaxations of mouse cavernosal tissue are m ediated by a transmitter which probably resembles an organic nitrate.