The present experiment was intended to study whether or not acetylcholine decreases the electrical resistance of the basal membrane of secretory cells in stimulating eccrine secretion of fluid and electrolytes. An isolated segment of the secretory coil of the monkey palm eccrine sweat gland was dissected out in vitro and immobilized in the tip of a constriction pipette. Using a bridge-balanced single glass microelectrode, input impedance of the secretory cell was compared before and after local superfusion of acetylcholine in each cell. The mean input impedance was 27 Momega, which did not significantly change after application of acetylcholine. Between 15 and 30 sec after cessation of acetylcholine superfusion, input impedance increased by 42% and then returned to normal within 60 sec. The current-induced voltage deflection due to intraluminally injected current pulse was measured across both the basal membrane (deltaVb) and the epithelial wall (deltaVt) as qualitative measures of the respective membrane resistances. Both deltaVb and deltaVt increased by about 10%, but their ratio remained unchanged after stimulation with acetylcholine. A Ca++ ionophore, A23187, which is as potent a stimulant of eccrine sweat secretion as acetylcholine in vitro, also failed to change the above two parameters. It was concluded that the decrease in the electrical resistance of the basal membrane of the secretory cells could not be detected in the sweat gland after stimulation with acetylcholine or A23187. The possibility was discussed that the action of acetylcholine at the basal membrane is one of enhancing the activity of the nonconductive pathway rather than the conductive pathway in this exocrine gland.
Acetylcholine Animals