Flow and potentials during perfusion of lacrimal gland with electrolyte solutions

Resting membrane potentials, acetylcholine (ACh)-induced change in membrane potentials of lacrimal gland cells, and ACh-induced flow from the excretory duct of the lacrimal gland were recorded during close intra-arterial perfusion of various electrolyte solutions. Resting membrane potentials were unchanged during perfusion with Na+-free, Cl--free, K+-free, and K+-rich solutions. Regardless of the composition of the perfusion solution, ACh induced hyperpolarization of the majority of cells but it also induced depolarization or biphasic potential or no change in potential in a significant number of cells. When the gland was perfused with a Na+-free or a Cl--free solution, the magnitude of the ACh-induced hyperpolarization was not changed but ACh-induced flow was markedly decreased. We conclude that the process(es) responsible for the ACh-induced change in potential may differ from those responsible for the ACh-induced flow and caution should be used when drawing conclusions about mechanisms of secretion solely from analysis of electrophysiological data.