Release of nitric oxide within the coeliac plexus is involved in the organization of a gastroduodenal inhibitory reflex in the rabbit

1. The coeliac plexus can organize a gastroduodenal inhibitory reflex witho ut action potentials. The involvement of the nitric oxide-cGMP pathway in t his reflex was investigated in the rabbit on an in vitro preparation of the coeliac plexus connected to the stomach and duodenum. Intraluminal duodena l pressures were measured with water-filled balloons. Gastric distension in hibited duodenal motility, thus characterizing a gastroduodenal inhibitory reflex organized by the coeliac plexus. 2. L-Arginine, superfused at the coeliac plexus level, enhanced this reflex , whereas N-omega-nitro-L-arginine (L-NOARG) or 2-(4-carboxyphenyl)-4,4,5,5 tetramethylimidazoline-1-oxyl-3-oxide (carboxy PTIO) reduced or abolished it. Moreover, diethylamine/nitric oxide complex superfused at the coeliac p lexus level inhibited duodenal motility in the absence of gastric distensio n. 3. The effects of nitric oxide were mediated through the activation of guan ylyl cyclase, as 1H-[1,2,4] oxadiazolo [4,3-a]quinoxalin-1-one (ODQ) reduce d or abolished the gastroduodenal inhibitory reflex, whereas zaprinast enha nced it. Moreover, 8-bromo-cGMP and cGMP, superfused at the coeliac plexus level, inhibited duodenal motility in the absence of gastric distension. 4. On the other hand, when superfused at the visceral level, L-NOARG, propr anolol plus phentolamine, and guanethidine did not affect the reflex. Thus, neither nitric oxide nor noradrenaline could be the transmitters released at the muscular level to induce this reflex. 5. Our study demonstrates that the gastroduodenal inhibitory reflex, which is organized by the coeliac plexus without action potentials, is induced by the release within the plexus of nitric oxide acting on the cGMP pathway T hese results provide new insights into the control of digestive motility by the prevertebral ganglia.