Evidence for the involvement of nitric oxide in the electrically induced relaxations of human lower esophageal sphincter and distal pylorus.

The aim of the present study was to investigate in vitro the effect of NG-nitro-L-arginine methyl ester (L-NAME), a nitric oxide (NO) synthase inhibitor, on neurogenic relaxation of human lower esophageal sphincter (LES) and distal pylorus (DP) circular muscle strips induced by electrical field stimulation (EFS). Muscle strips obtained from 5 patients who underwent total gastrectomy were suspended in 10-ml organ baths containing Krebs solution for recording isometric tension. L-NAME (30 microM) reduced the amplitude of the EFS-induced relaxation by 85 +/- 9% (N = 3) in the LES and by 52 +/- 16% (N = 3) in the DP but did not affect sodium nitroprusside-induced relaxation. L-Arginine (300 microM) partially reversed the L-NAME inhibition in the LES and totally in the DP. These findings suggest a role for L-arginine-derived NO in the nerve-mediated NANC relaxation of the human LES and DP.