Stimulation by carbachol of mucus gel thickness in rat stomach involves nitric oxide.

Instillation of carbachol (150 micrograms/kg) into the gastric lumen in vivo increased the thickness of the mucus gel layer. Intravenous administration of the inhibitor of nitric oxide (NO) synthase, NG-nitro-L- arginine methyl ester (L-NAME, 0.4-5 mg/kg) dose-dependently reduced the stimulation by carbachol, the half-maximal inhibitory dose being 0.57 mg/kg. This effect of L-NAME was abolished by administration of L-arginine but not by D-arginine (100 mg/kg i.v.). By contrast L-NAME (5 mg/kg) did not reduce the stimulatory effect of intraluminal 16,16-dimethyl prostaglandin E2 (50 micrograms/kg) on mucus gel thickness. These results implicate NO in the cholinergic activation of gastric mucus secretion.