Electrical spiking activity and propulsion in small intestine in fed and fasted rats.

Bipolar electromyograms were obtained from electrodes chronically implanted on the small intestine in rats accustomed to receiving food only during 4 days per week. Continuous recording, begun 5 to 10 days after operation, continued for 10 to 15 days. The spiking activity was continuously summed at 20-sec intervals on linear integrators. At the end of the experiment, small intestinal propulsion and gastric emptying were measured. During fasting, the pattern of spike bursts of the jejunum was a cycle of three phases: a period of silence was followed sequentially by periods of irregular and regular spike bursts, lasting 6 to 10 min and 4 min, respectively. Cycles recurred at intervals of 16 to 20 min and migrated caudad at 2 to 3 cm per min. Intragastric administration of food and amino acids caused continuous irregular spiking for 2 to 3 hr. A similar effect resulted from amino acids and glucose administered into the duodenum. Continuous but weak irregular spiking followed intragastric or intraduodenal administration of oleic acid. In fasted rats, the velocity of intestinal transit was faster when a bolus was administered before a migrating complex than after Marker movement was rapid in fed rats in whom there was continuous irregular spiking. The presence of nutrients in the intestinal lumen alters the patterns of contractions.