Determination of acetylcholine null potential in mouse pancreatic acinar cells

Abstract

PERHAPS the most important parameter of transmitter action is the value of the membrane potential at which no potential change occurs after excitation. This value is termed the transmitter null (equilibrium) potential (refs 1 and 2 and refs therein). The determination of this value requires the use of two intra-cellular electrodes, one for recording the cell membrane potential and the other for passing current to set the membrane potential at appropriate levels. In addition it requires the availability of reproducible short lasting applications of transmitter. The recent demonstration that the pancreatic acinus functions as one electrical unit, that is that unimpaired electrical communication between neighbouring acinar cells exists^3,4, makes it possible to treat the acinus as one cell. By combining insertion of two electrodes into one acinus with local iontophoretic application of acetylcholine (ACh) from a third extracellular microelectrode, we have measured directly the null potential for the action of a neurotransmitter on mammalian gland cells.