Intracellular Ca2+ injection causes membrane hyperpolarization and conductance increase in lacrimal acinar cells.

Membrane potential and resistance measurements were carried out on segments of superfused mouse exorbital lacrimal glands by inserting two microelectrodes into neighbouring coupled cells. Short-lasting intracellular injections of Ca2+, by the method of microiontophoresis, caused membrane hyperpolarization and resistance reduction. These effects were also observed in the presence of adrenergic and cholinergic blocking agents. From the potential and resistance changes observed the null potential for the action of Ca2+ was calculated to be -50 mV. Short-lasting extracellular Ca2+ applications caused membrane hyperpolarization and resistance reduction, but these effects were blocked by a combination of atropine and phentolamine. Intracellular Ca2+ application mimics the action of adrenaline and acetylcholine on lacrimal acinar cells.