Effects of the Parasympathomimetic Drug Methacholine and Its Antagonist Atropine on Mucociliary Activity

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Abstract
The effect on the mucociliary (m.c.) activity of the parasympathomimetic drug methacholine and its antagonist atropine was studied with the aid of a newly developed rabbit test model, designed for evaluating the effect of pharmacological substances on the m.c. wave frequency. Methacholine i.a. [intraarterially] (0.01-2 .mu.g/kg) gave a dose-dependent acceleration of the m.c. wave frequency, and the threshold dose 0.03 .+-. 0.02 .mu.g/kg is suggested to be within physiological limits. The anticholinergic drug atropine i.a. (0.05-0.5 mg/kg) did not influence the basal m.c. wave frequency, but a dose of 0.2 mg/kg reduced or abolished the responses to methacholine (0.05-2 .mu.g/kg). Evidently, the basal m.c. activity functions independently of parasympathetic activity in anesthetized animals, parasympathomimetic drugs influence the m.c. activity and the effects of these drugs can be reduced or blocked by atropine.