The Electrophysiology of the Submaxillary Gland of the Cat.

Summary. The electrophysiology of the submaxillary gland of the cat has been studied with external and intracellular electrodes. The external chorda electrogram led off between the hilus and the free surface of the gland is not constant except for the initial, fast hilus‐positivity. After this initial phase, a slow phase appears, which may be hilus‐negative or, as in the sympathetic electrogram, hilus‐positive. When recording over the duct wall inside the hilus, stimulation of the chorda or of the sympathetic nerve results in negativity of the duct interior. The time course of this potential change resembles that of the slow phase of the respective external electrogram. In experiments with microelectrodes, three types of responses were identified, the differentiation depending on the magnitude of the membrane potential, as well as on the sign and time course of the potential change occurring on stimulation of the secretory nerves. It is assumed that these potentials are recorded from single cells. Response type I, originating from gland cells, has a resting potential over the outer membrane of about 22 mV (cell interior negative). Stimulation of either of the secretory nerves increases the potential over the outer membrane to 45—60 mV, the latency and time course of this increase being similar to that of the initial phase of the external electrogram. It is suggested that the direction of current flow signifies that the lumen of the acinus is becoming positive to the cell interior. Response type II, with a resting membrane potential of about 33 mV, is less often found. Single shocks to the chorda increase the internal negativity for 7—10 sec., whereas repetitive stimulation of the sympathetic nerve results in decreased internal negativity. There is no indication that these potentials have any equivalents in the external electrogram. Response type III, with a resting internal negativity of 80 mV, is found only in the depth of the gland. Stimulation of either of the secretory nerves decreases this internal negativity, the time course being similar to that of the potential change recorded over the wall of the duct. It is suggested that this response originates from the cells of the striated tubuli, and that in addition to the potential change over the outer membrane directly measured, there is at activity also a potential change over the inner membrane with the sign that the lumen becomes negative to the cell interior. The significance of these findings with respect to the mechanism of secretion and of problems concerning the innervation of gland cells is discussed.