The effects of diabetes on nitric oxide-mediated responses in rat corpus cavernosum

Nitric oxide (NO)-mediated responses were investigated in corpora cavernosa isolated from 8-week diabetic rats. Relaxations to field stimulation were abolished by N-G-nitro-L-arginine (NOARG, 100 mu M). Responses to stimulati on and sodium nitroprusside were reduced in tissues from diabetic rats comp ared to control rats, when data were expressed as g tension, but not when e xpressed as g/g tissue. The endothelium-dependent vasodilator, acetylcholin e, failed to relax tissues. Stimulation-induced contractions were smaller i n the diabetic group compared to the control group when data were expressed as g tension, but not g/g tissue. Contractions were enhanced by NOARG, and inhibited by acetylcholine (300 mu M), by a similar degree in both groups. NOARG reduced the inhibitory effect of acetylcholine in tissues from contr ol, but not diabetic rats. The results suggest diabetes caused a general im pairment in responsiveness of rat corpus cavernosum, which may be a consequ ence of tissue weight change. A role for endothelium-dependent NO could not be identified; however, NO-mediated modulation of noradrenergic transmissi on by acetylcholine, may be defective in diabetes. (C) 1999 Elsevier Scienc e B.V. All rights reserved.