The Action Potentials of the Stomach

The potential changes associated with the conduction of impulses in muscle and nerve can be interpreted only if they are led off from small regions of the tissue. This is accomplished most satisfactorily by recording monophasic potentials or by recording the potentials in the intact tissue with differential electrodes. In the study of the stomach only tJhe second of these methods is practical. However, as shown by Cole and Curtis (7), the differential potential is the first derivative of the monophasic potential provided the distance between the leads is appreciably less than the length of the active region. It is possible, therefore, to derive the monophasic potential mathematically. It is important to realize that missible for recording differential the maximal potentials is and that it must be the smaller, the muscle the waves are shorter than distance between the leads per-not the same for different tissues shorter each in any other wave of excitation. In smooth tissue studied. Therefore, the leads should be very small and their distance should be preferably less than one millimeter. Some events of the action potential of smooth muscle, like the rising phase or spike potentials, take up a width of less than one millimeter (5) and such events cannot be resolved accurately with the methods available at a the present time. For illustration, the may be mentioned (p. 697). During potentials of the stomach of the each peristaltic wave, as many as P% guinea twenty spikes can be observed. Since the active region, as seen by direct observation, is less than one centimeter wide, the spikes are spaced on the muscle at a distance of less than half a millimeter. The failure to recognize this point, the use of large electrodes separated one centimeter or more, largely explains why previous investigators obtained widely disagreeing results and why their records show such marked variability. Records obtained by Alvarez and Mahoney (2) with a slow galvanometer show no resemblance to those which will be described below. Richter (9) using a string galvanometer and monopolar (not monophasic) leads recorded during each contraction several slow waves, beginning with a positive deflection. Two of these waves undoubtedly are identical with the R and T wave described below. METHOD. Dogs (5-7 kgm.), cats and guinea pigs anesthetized with nembutal were used. The abdomen of the animal was inside a heated and humidified chamber. The stomach was exposed by a longitudinal …