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 incontrol of pyloric function and transpyloric flow wereinvestigated in six conscious dogs. Antropyloroduodenalmotility, transpyloric flow, and gastric emptying were measured 15 min after intravenousinjection of 100 ml of either saline, L-arginine (50mg/kg), L-NNA (5 mg/kg), or L-arginine (50 mg/kg)followed by L-NNA (5 mg/kg). Infusion of L-NNA wasassociated with retardation of gastric emptying (65± 6%) in the first 30 min, in comparison to thesaline (90 ± 3%) or L-arginine (90 ± 2%).This effect was prevented by infusion of L-arginineprior to L-NNA, after which 89 ± 3% of the liquidemptied in 30 min. There was a significant reduction (P< 0.05) in the number and volume of flow pulses, andan increase in pyloric tone (P < 0.05) after L-NNA in comparison to the other three testconditions. There were no differences, however, in thenumber of antropyloric or isolated pyloric pressurewaves under the four conditions. Our findings suggestthat NO mechanisms influence gastric emptying andtranspyloric flow of nonnutrient liquids by altering thepyloric tone, thus increasing resistance toflow.