ROLE OF NITRIC-OXIDE MECHANISMS IN CONTROL OF PYLORIC MOTILITY AND TRANSPYLORIC FLOW OF LIQUIDS IN CONSCIOUS DOGS

The role of nitric oxide (NO) mechanisms in control of pyloric functio n and transpyloric flow were investigated in six conscious dogs. Antro pyloroduodenal motility, transpyloric how, and gastric emptying were m easured 15 min after intravenous injection of 100 mi of either saline, L-arginine (50 mg/kg), L-NNA (5 mg/kg), or L-arginine (50 mg/kg) foll owed by L-NNA (5 mg/kg). Infusion of L-NNA was associated with retarda tion of gastric emptying (65 +/- 6%) in the first 30 min, in compariso n to the saline (90 +/- 3%) or L-arginine (90 +/- 2%). This effect was prevented by infusion of L-arginine prior to L-NNA, after which 89 +/ - 3% of the liquid emptied in 30 min. There was a significant reductio n (P < 0.05) in the number and volume of flow pulses, and,an increase in pyloric tone (P < 0.05) after L-NNA in comparison to the other thre e test conditions. There were no differences, however, in the number o f antropyloric or isolated pyloric pressure waves under the four condi tions. Our findings suggest that NO mechanisms influence gastric empty ing and transpyloric flow of nonnutrient liquids by altering the pylor ic tone, thus increasing resistance to flow.