Nitric oxide released by gastric mechanoreceptors modulates nicotinic activation of coeliac plexus neurons in the rabbit

The effects on the nicotinic activation of the coeliac plexus neurons of ni tric oxide (NO) released within the coeliac plexus by gastric mechanorecept ors, in particular during gastroduodenal inhibitory reflex, were assessed. This study was performed in the rabbit on an in vitro preparation of the co eliac plexus connected to the stomach and the duodenum. The electrical acti vity of ganglionic neurons was recorded with intracellular recording techni ques. Water-filled balloons were used for gastric distensions and recording of duodenal motility. When a 10-s train of pulses (20-40Hz) of supramaxima l intensity was applied to the splanchnic nerves, gradual depression of nic otinic activation occurred. Gastric distension (50 mL, 7.5 min) modulated t his depression phenomenon by inhibiting or facilitating the nicotinic activ ation. In the neurons impaled during the recording of duodenal motility, ga stric distension triggered an inhibition of nicotinic activation concomitan tly with a gastroduodenal inhibitory reflex organized by the coeliac plexus . If the gastric distensions were performed while the coeliac plexus was su perfused by a NO scavenger, the nicotinic activation was unaffected and the gastroduodenal inhibitory reflex was abolished. Moreover, when the coeliac plexus was superfused with an inhibitor of nitric oxide synthase, gastric distensions were without effect on the nicotinic activation. These results demonstrate that NO released within the coeliac plexus by gastric mechanore ceptors, in particular during the gastroduodenal inhibitory reflex, modulat es the central nicotinic activation of coeliac plexus neurons, so NO releas ed within a prevertebral ganglion by gastric afferent fibres, in particular during the organization by this ganglion of a reflex regulating the gastro intestinal tract motility, also exerts a gating of the central inputs to th e ganglionic neurons.