Effects of various treatments on GB0710-induced relaxation in the phenylephrine (5×10−6 mol l−1)-induced precontracted rabbit isolated corpus cavernosum smooth muscle strip. The relaxation effect of GB0710 was partially inhibited by endothelial disruption and by pretreatment with methylene blue (10−4 mol l−1), pyrogallol (10−4 mol l−1), L-NNA (3×10−4 mol l−1), or 1H-[1,2,4] ODQ (5×10−6 mol l−1). Values are represented as mean±standard error and expressed as percentage of the relaxation. *P<0.05, the difference between treatment and control by Mann–Whitney U test. L-NNA, NG-nitro-L-arginine; ODQ, oxadiazolo-[4, 3-α] quinoxalin-1-one.