Effects of anesthesia and surgical procedures on intestinal myoelectric activity in rats

Electrical spiking activity of the duodenum and jejunum was recorded from chronically implanted electrodes in rats during volatile or barbiturate anesthesia and following laparotomy. The normal pattern of electrical spiking activity in the fasted rat, with myoelectric complexes at 15-min intervals, was transiently replaced by quiescence during ethyl ether anesthesia. A slight increase in irregular spiking activity occurred after induction with pentobarbital, and the only effect of thiopental anesthesia was a reduction in the velocity of propagation of the complexes by 20%. Under barbiturate anesthesia, incision of the skin did not inhibit myoelectric activity, but incision of each abdominal muscle layer had an immediate and transient inhibitory effect; the deeper the layer, the longer was the inhibition. Peritoneal incision consistently produced inhibition of spiking activity which was prolonged by exposure of the bowel to air and intestine handling. The inhibitory effects produced by surgery persisted after vagotomy or transection of the spinal cord at the thoracic level but disappeared after splanchnicectomy. The above results suggest that a somatovegetative reflex with efferent pathways in the splanchnic nerves is involved in the first stage of operative inhibition of intestinal myoelectric complexes.