Effects of sympathomimetic agonists and antagonists on mucociliary activity.
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 beta-adrenoceptor agonist isoprenaline (0.005-10 micrograms/kg i.a.) and the selective beta2-adrenoceptor agonist salbutamol (0.01-10 micrograms/kg, i.a.) induced a dose-dependent acceleration of the m.c. wave frequency, whereas the beta1-adrenoceptor agonist prenalterol (1-200 micrograms/kg, i.a.) did not influence the basal m.c. activity. The selective alpha1-adrenoceptor agonist phenylephrine (0.01-20 micrograms/kg, i.a.) and the selective alpha2-adrenoceptor agonist oxymetazoline (0.001-1 microgram/kg, i.a.) both induced a dose-dependent retardation of the m.c. wave frequency. The non-selective beta-adrenoceptor antagonist propranolol (2-200 micrograms/kg, i.a., and 1 mg/kg, i.v.) and the non-selective alpha-adrenoceptor antagonist phentolamine (0.1-1 000 micrograms/kg, i.a.) had no influence on the basal m.c. wave frequency. Propranolol (1-2 mg/kg, i.v.) reduced the effect of isoprenaline and salbutamol (both in the dose range of 0.01-10 micrograms/kg, i.a.) and similarly phentolamine (0.2 and 1 mg/kg, i.a.) reduced the effect of oxymetazoline (0.01-10 microgram/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 beta2-adrenoceptors accelerate the wave frequency, whereas sympathomimetic agonists acting on alpha1 and alpha2-adrenoceptors have a retarding effect, all in a dose-dependent manner.