The effect of isoprenaline on the ciliary activity of an in vitro preparation of rat trachea.

A dose dependent increase in the ciliary beat frequency of rat tracheal explants was found over a 10(-7)-10(-3) M concentration range of (+/-)-isoprenaline and was abolished by 10(-7) M propranolol. Furthermore (+)-isoprenaline, a drug which is much less potent in its action on beta-adrenoceptors than its (-)-isomer, failed to cause a stimulation. We conclude that the acceleration in the intrinsic ciliary beat frequency by (-)-isoprenaline, although occurring at a relatively high concentration compared with the action of the drug on other tissues, is mediated by beta-adrenoceptors.