Regulation of tear secretion.

Although many questions remain about the regulation of secretion by the different layers of the tear film, several hypotheses can be suggested. We hypothesize first, that secretion of all layers of the tear film and all orbital glands and ocular epithelia that secrete tears is regulated; second, that neural regulation of secretion is of primary importance; and third, that the cAMP-dependent signal transduction pathway plays a pivotal role in this regulation and, except in the main lacrimal gland, Ca2+ plays a secondary role. These hypotheses are suggested as the basis for further work and not as conclusions based on current knowledge.