Effects of ethanol and other aliphatic alcohols on NO‐mediated relaxations in rat anococcygeus muscles and gastric fundus strips

In anococcygeus muscles, ethanol (20–500 mm) slightly increased the tone and inhibited relaxations elicited by nitrergic nerve stimulation (0.5–5 Hz) in a concentration‐dependent manner. Other aliphatic alcohols decreased the tone but had inhibitory effects similar to ethanol on stimulation‐induced relaxations, the EC₅₀ (mm) values being: methanol 280, ethanol 80, propan‐1‐ol 20, propan‐2‐ol 55, propan 1,2‐diol 135, butan‐1‐ol 120, butan‐2‐ol 15 and pentan‐1‐ol 3. Relaxations induced by sodium nitroprusside (SNP, 10 nm) were inhibited by ethanol (20–500 mm) in a concentration‐dependent manner and by propan‐2‐ol (100 mm). Relaxations induced by NO (1 μm) were inhibited by high concentrations of ethanol (200–300 mm) and by propan‐2‐ol (100 mm). In gastric fundus strips, ethanol (60–200 mm) did not affect the resting tone but inhibited NO‐mediated relaxations elicited by low frequency (1 Hz) field stimulation and reduced the initial relaxation by high frequency field stimulation (10 Hz) and by SNP (50 nm). The relaxant action of isoprenaline (10 nm) was not reduced although it was slightly slower in onset. Other aliphatic alcohols tested decreased the tone and inhibited relaxations elicited by field stimulation. Acetaldehyde (1–10 mm) inhibited relaxations elicited by field stimulation and SNP in both the rat anococcygeus muscles and gastric fundus strips. The tone of gastric fundus strips was decreased by acetaldehyde but it was transiently increased in anococcygeus muscles. The dehydrogenase inhibitors, 4‐methylpyrazole (100 μm) and disulfiram (100 μm) did not significantly affect the inhibition by ethanol of nitrergic nerve stimulation‐induced relaxations in anococcygeus muscles, which suggests that ethanol acts directly. The inhibition of NO‐mediated relaxations by alcohols is attributed to sequestration of NO to form nitroso‐alcohols. 1994 British Pharmacological Society