Effects of Sympathomimetic Agonists and Antagonists on Mucociliary Activity

Abstract

The effect on the mucociliary (m.c.) wave frequency of sympathomimetic agonists and antagonists was studied in the maxillary sinus in anesthetized rabbits. The non-selective β-adrenoceptor agonist isoprenaline (0.005–10 µg/kg, i-a-) and the selective β₂-adrenoceptor agonist salbutamol (0.01–10 µg/kg, i.a.) induced a dose-dependent acceleration of the m.c. wave frequency, whereas the β₁-adrenoceptor agonist prenalterol (1–100 µg/kg, i.a.) did not influence the basal m.c. activity. The selective aradrenoceptor agonist phenylephrine (0.01–20 µg/kg, i.a.) and the selective α₂-adrenoceptor agonist oxymetazoline (0.001–1 µg/kg, i.a.) both induced a dose-dependent retardation of the m.c. wave frequency. The non-selective β-adrenoceptor antagonist propranolol (2–200 µg/kg, i.a., and 1 mg/kg, i.v.) and the non-selective α-adrenoceptor antagonist phentolamine (0.1–1000 µ/kg, i.a.) had no influence on the basal m.c. wave frequency. Propranolol (1–2 mgJkg, i.v.) reduced the effect of isoprenaline and salbutamol (both in the dose range of 0.01–10 µg/kg, i.a.) and similarly phentolamine (0.2 and 1 mgJkg, i.a.) reduced the effect of oxymetazoline (0.01–10 µg/kg, i.a.).

It was concluded that during basal conditions in the anesthetized rabbit the m.c. activity functions independently of sympathetic activity and that sympathomimetic agonists acting on β₂-adrenoceptors accelerate the wave frequency, whereas sympathomimetic agonists acting on α₁ and α₂-adrenoceptors have a retarding effect, all in a dose-dependent manner.