Autonomic control of lacrimal protein secretion

The ability of cholinergic and adrenergic agonists to initiate protein secretion by in vitro slices of rabbit lacrimal gland was examined. The adrenergic response was not inhibited by atropine but was partially inhibited by propranolol and phentolamine. This indicates the presence of both alpha- and beta-adrenergic receptors and their association with the protein secretory response. The cholinergic response was inhibited completely by the muscarinic antagonist atropine. Additionally, the adrenergic antagonists, propranolol and phentolamine, inhibited approximately 70% and 40%, respectively, of the cholinergic response. Dose-response curves obtained for carbachol and isoproterenol indicated that the maximum response to carbachol is greater than that to isoproterenol but that the threshold for response to isoproterenol is much lower than that to carbachol. Additionally, carbachol and isoproterenol acted synergistically in promoting protein secretion. A hypothesis for the regulation of lacrimal gland function is proposed which takes into account the autonomic effects on electrolyte transport and tear flow rates reported by others as well as autonomic control of protein secretion reported in this paper.