Abstract
The present investigation was undertaken because previous reports about the effects of sympathomimetics upon lacrimation were based upon methods which were indirect, insensitive, and nonspecific since they measured indiscriminately the activity of all glands that contribute to the formation of tears. In this study the excretory duct of the inferior lacrimal gland of the rabbit was cannulated under pentobarbital anesthesia and flow of lacrimal fluid was measured with a recording flowmeter. Femoral artery pressure and the electrocardiogram toere recorded continuously and simultaneously with lacrimal gland flow. The results may be summarized as follows: (1) After intravenous pilocarpine (0.1 mg. per kilogram) there was an immediate increase in flow tohich, at maximum, was eleven times the control rate and which persisted for 33 minutes. (2) Intravenous norepinephrine (10 fig per kilogram), after a 30 second delay, produced an elevation of flow that persisted for 2 minutes and which, at maximum, toas three times the control rate. (3) When intravenous norepinephrine ivas preceded by an intravenous dose of pilocarpine, norepinephrine caused a significant depression which was followed by an increase in flow similar to that obtained with norepinephrine alone. (4) Local intra-arterial injections of pilocarpine (0.5 mg. per kilogram) and norepinephrine (5 µg per kilogram) produced results similar to those produced by intravenous injections.