Inhibition and facilitation of lacrimal flow by beta-adrenergic drugs

The effects of adrenergic beta-stimulating and beta-blocking compounds on tear flow were studied in conscious rabbits with a modified Schirmer technique. The tear flow was significantly increased by the unselective beta-adrenergic agonist isoprenaline and by the selective beta1-agonist H 80/62 (racemic Prenalterol, Hässle, Sweden). The effects of the agonists were blocked by the unselective beta-adrenergic antagonist propranolol (Inderal) and by the selective beta1-antagonist metoprolol (Seloken, Lopressor). The experimental data favoured the hypothesis that the beta-receptors involved in the regulation of the tear flow were of the beta1-type. The anatomical location of these beta-receptors is at present unclear but in vitro experiments performed on the rabbit lacrimal glands indicated that the receptors were probably not located on cholinergic nerve-endings as the release of acetylcholine was not influenced by isoprenaline.