EFFECT OF NITRIC-OXIDE ON PROPAGATED CLUSTERS OF SPONTANEOUS MOTOR WAVES IN AN EX-VIVO RABBIT INTESTINAL PREPARATION

The aim of this study was to determine whether nitric oxide can play a role in regulating the propagation of spontaneous motor activity in a rabbit intestinal preparation completely excluded from any central an d vascular connection. Experiments were done on nine rabbits of either sex, weighing 2.5 +/- 0.5 kg (mean +/- SD). After one week of semiliq uid diet the animals were sacrificed and a segment including the stoma ch, duodenum and part of the jejunum was removed and placed into a sin gle chamber organ bath containing I L of oxygenated Krebs' solution. F our strain gauges connected to a Dynograph Recorder were sutured on th e serosal surface 10 cm apart starting from the gastric antrum to the distal duodenum. Once the motor activity was stabilized N-nitro-L-argi nine methyl-ester (L-NAME) was added to the bath at increasing concent ration from 10(-7) to 10(-4) M. Spontaneous motor activity was recorde d, characterized by the cycling occurrence of bursts of waves, startin g from the stomach and propagating to the descending duodenum. L-NAME at higher concentrations reduced the time interval between the bursts of waves with a concomitant increase in the propagation velocity of th e motor activity. No change in the frequency of waves was detected. Th e effect of L-NAME was prevented by the administration of L-Arginine. This study suggests an important role for the nitric oxide pathway in the distal propagation of the spontaneous motor activity of the alimen tary tract.