Electrical activity of the small intestine of man and of dogs has been studied using monopolar recording techniques and spread of electrical activity in the small intestine of the dog using a bipolar recording technique. Motility was studied simultaneously. Electrical activity consisted of slow waves and action potentials which occurred when contractions were present. Action potentials were not conducted but slow waves sometimes spread aborally for short distances. Particular attention was paid to the relation of slow waves to action potentials and to motility. No consistent alteration in the frequency or configuration of slow waves was found associated with the occurrence of action potentials and motility, although serotonin or epinephrine altered slow wave frequency slightly. Slow waves usually were increased in amplitude during periods when motility and action potentials were occurring (during eating or balloon propulsion; after the administration of serotonin, neostigmine, physostigmine, or morphine). Slow wave amplitudes usually were diminished when motility was inhibited (by balloon distention; after administration of epinephrine, etc.). Action potentials tended to occur in phase with the slow waves, when the muscle electrode was positive relative to the indifferent electrode, but this was not always so during nonpropulsive contractions. There was also a correlation between the occurrence of distal spread of slow waves over the duodenum and upper jejunum and the ability of the intestine in this region to respond to balloon distention by propulsion.In the dog, body temperature consistently affected slow waves. A decrease of 10 °C diminished their frequencies to less than one-half and diminished their amplitude. Slow waves occurred at similar frequencies and with regular conduction after large doses of nicotine or atropine. Dibenzyline, dichloroisopropyl-norepinephrine, and vagotomy did not markedly alter slow wave frequencies. These findings and those in our studies with microelectrodes indicate that the slow waves are myogenic in origin, and represent electrical currents in the extracellular fluid initiated by periodic depolarizations of muscle cells of the small intestine.
