Evidence for the requirement of sympathetic activity in the PGE<inf>1</inf>-induced lacrimal secretion in rabbits

Abstract

The effect of prostaglandin E1 (PGE1) administered either intraarterially or intravenously on basal fluid secretion from the lacrimal gland after various treatments was studied in anaesthetized rabbits. Intraarterial administration of either propranolol (1 mg/kg) or phentolamine (1 mg/kg) effectively prevented secretion induced by PGE1 but not by methacholine. Pretreatment with hexamethonium (1 mg/kg) markedly inhibited PGE1-mediated lacrimal flow whereas methacholine-induced secretion was not affected. The secretory response to PGE1 was completely blocked after section of postganglionic fibres of the ipsilateral superior cervical sympathetic ganglion. On the other hand, preganglionic sympathectomy had no effect on secretion evoked by PGE1. The effect of PGE1 was independent of the route of administration. The results are discussed in terms of stimulation of postganglionic sympathetic nerves by PGE1 to release noradrenaline. The latter, in turn, elicits fluid secretion by a process (or processes) involving activation of β-receptors, most likely, on the secretory acinar cells.