The effect of cecal volume change on gastric motility in rats.

The effect of a change in cecal volume on gastric motility was studied in 24 h fasted rats anesthetized with urethane (0.8 g/kg, i.p.). A cecal volume increase from 1 to 10 ml (in 1 ml steps) produced a decrease in the basal tone of the stomach. The maximal inhibitory response was produced with an 8 to 10-ml increase in cecal volume. The gastric inhibitory response continued as long as the increased cecal volume was maintained. It was abolished by a combination of a splanchnicotomy and vagotomy, or only a splanchnicotomy in a few cases. The inhibition of gastric motility by increasing the cecal volume also occurred after severance of dorsal roots between T8 and L4 and gastric branches of vagus nerves. It is suggested that an increase in cecal volume induces gastric relaxation mainly via the splanchnico-splanchnic pathway and partly via the vago-vagal and vago-splanchnic pathways. Therefore, retardation in transit of the gastric contents in germ free rats having an enlarged cecum may be attributed to an enhancement of the ceco-gastric inhibitory reflex. The ceco-gastric inhibitory response mediated by the splanchnic pathway was abolished by guanethidine (3-5 mg/kg, i.v.), but the response mediated by the vagal pathway was resistant to guanethidine as well as to atropine (0.2 mg/kg, i.v.). This result indicates that splanchnic postganglionic efferents are adrenergic, while vagal postganglionic efferents are non-adrenergic and non-cholinergic.