Electrical activity in an exocrine gland: optical recording with a potentiometric dye.

Propagated action potentials in the salivary gland of a freshwater snail were detected by optical means. Voltage-dependent absorption changes from acinar cells stained with a merocyanine-oxazolone dye faithfully reproduced the time course of electrical activity in this tissue. Such signals may provide a useful tool for the study of endocrine tissue as well.