Differential significance of nitric oxide in hypotensive mechanisms of acetylcholine and histamine in dogs.

The nitric oxide synthase inhibitor, NG-nitro-L-arginine, suppressed hypotensive response to acetylcholine, but not to histamine, in pentobarbital-anesthetized dogs. Infusions of acetylcholine increased plasma cyclic GMP levels, while histamine infusions did not. These results indicate that there is an apparent difference in the contributions of nitric oxide to the hypotensive mechanisms of acetylcholine and histamine.