Endothelium-Derived Relaxing Factors From Acetlcholine in Cerebral Vessels in Cats

Background and Purpose: The predominant view is that the endothelium-derived relaxing factor generated by acetylcholine from blood vessels is nitric oxide. However, there is evidence suggesting that certain nitric oxide-containing compounds such as nitrosothiols resemble the endothelium-derived relaxing factor generated by acetylcholine more closely than does nitric oxide itself. Accordingly, we compared the effects of nitric oxide and S-nitroso-L-cysteine on cerebral arteriolar caliber in relation to the associated increments in nitrite concentration in the effluent. Methods: Acetylcholine, nitric oxide, and S-nitroso-L-cysteine were administered by continuous superfusion in oxygen-free solution through the space under a cranial window in anesthetized cats. Nitrite concentration was measured in the effluent. The degree of vasodilation induced was evaluated in relation to the increment in nitrite concentration. Results: All agents induced dose-dependent vasodilation and dose-dependent increments in nitrite concentration in the effluent. For any given degree of vasodilation, the increments in nitrite concentration