Pirenzepine and exocrine secretions: a selective agent for gastric glands?

Nineteen healthy volunteers were studied to investigate whether or not muscarinic receptors of different exocrine glands could be distinguished from one another by the use of pirenzepine. A simultaneous evaluation of lacrimation, salivation and gastric secretion was carried out, bethanechol (80 micrograms/kg/hr) being used as a stimulant and pirenzepine (10 or 5 mg i.v.) as an inhibitor. Bethanechol increased salivation significantly and the volume of gastric juice, and non-significantly increased lacrimation and total acid output. Pirenzepine abolished the hypersecretion induced by bethanechol, and decreased the basal level of the exocrine secretions, to approximately the same extent. These experiments seem to demonstrate that if there is a difference among the muscarinic receptors of lacrimal, salivary and gastric oxyntic glands, pirenzepine is unable to discriminate them from one another, at least under the experimental conditions of this investigation.