Stimulation of rabbit lacrimal gland secretion with biologically active peptides.

To determine whether biologically active peptides can stimulate lacrimal gland secretion, we measured fluid and protein secretion from the cannulated lacrimal gland excretory duct of anesthetized rabbits after arterial injection of various peptides. Vasoactive intestinal peptide (VIP, 0.003-3 nmol) and porcine histidine isoleucine-containing peptide (PHI, 0.01-3 nmol) stimulated fluid and protein secretion in a dose-dependent manner. Cholecystokinin octapeptide (CCK-8, 0.01-3 nmol) stimulated fluid but not protein secretion. Neither bombesin nor eledoisin in doses as high as 3 nmol stimulated fluid or protein secretion. When combinations of high or low doses of VIP and the cholinergic agonist acetylcholine (ACh) were injected simultaneously, fluid and protein secretion was additive. We concluded that VIP and PHI stimulated secretion of lacrimal gland fluid and protein, CCK-8 stimulated secretion of fluid, and bombesin and eledoisin did not stimulate either fluid or protein secretion. VIP and ACh, both found in lacrimal gland nerve endings, stimulate lacrimal gland fluid and protein secretion by separate pathways.