Vago-Vagal Reflex Relaxation of the Stomach in the Cat

In acute experiments on chloralosed cats gastric motility was recorded with a rubber balloon system kept at constant intragastric pressure under experimental conditions not requiring abdominal surgery.-Electric stimulation of the central end of either a small vagal branch at the level of the diaphragm or of one vagal nerve at the level of the neck, while the opposite vagal nerve was left intact produced profound reflex relaxation of the stomach. Also the efferent pathway of the relaxatory reflex was in the vagal nerves.-The reflex relaxation persisted after administration of atropine, which shows that it was not due to reflex suppression of prevailing activity of the vagal cholinergic motor fibres. It was also independent of adrenergic mechanisms, since it persisted after administration of guanethidine in doses known effectively to block the adrenergic intestino-gastric inhibitory reflex. This vago-vagal relaxatory reflex response thus showed the same characteristics as the gastric response elicited by efferent stimulation of the high-threshold vagal relaxatory fibres.-It is concluded that this vago-vagal reflex originates, at least partly, from abdominal structures, with the efferent pathway consisting of the relaxatory, high-threshold fibres producing pronounced gastric relaxation. This vago-vagal relaxatory reflex may be involved in receptive relaxation of the stomach.