Spino-Vagal Nonadrenergic Inhibition of Gastric Motility Elicited by Abdominal Nociceptive Stimulation in the Cat

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Abstract
Reflex inhibition of gastric motility in response to intestinal nociception and afferent nerve stimulation was studied in anesthetized cats. Mechanical stimulation of the small and large intestines elicited marked gastric inhibition, which was imitated by direct electrical stimulation of mesenteric or splanchnic afferents. The reflex response was resistant to atropine, guanethidine, and adrenalectomy. Spinal cord transection at the cervical level or spinal anesthesia completely blocked the reflex, as did vagotomy or vagal cold blockade. Chemical peritoneal stimulation by hydrochloric acid induced long-lasting gastric inhibition, which was not blocked by antiadrenergic or anticholinergic drugs. This response was reduced, but not completely blocked by spinal anesthesia or spinal cord transection. It is concluded that various nociceptive intestinal stimuli suppress gastric motility via a spino-vagal reflex mechanism composed of spinal afferents in the sympathetic nerves, spinobulbar ascending pathways, and vagal nonadrenergic inhibitory fibers to the stomach. In addition, vago-vagal reflexes evidently contribute to the gastric suppression induced by diffuse peritoneal irritation. These two reflex mechanisms are suggested to be mainly responsible for postoperative gastric inhibition, together with sympatho-adrenergic reflexes.