ERYTHROMYCIN INHIBITS CHOLINERGIC NEUROEFFECTOR TRANSMISSION IN CANINE AIRWAY SMOOTH-MUSCLE

To elucidate whether macrolide antibiotics affect cholinergic neuro-effector transmission in the airway, we studied canine isolated bronchial segments under isometric conditions in vitro. Addition of erythromycin (3 x 10(-4) M) attenuated the contractile responses to electrical field stimulation (EFS), so that the stimulus frequency required to produce a half-maximal contraction (ES(50)) increased from 1.3 +/- 0.3 to 5.1 +/- 0.5 Hz p < 0.001). This effect was concentration-dependent and not influenced by propranolol, indomethacin, ouabain or mechanical removal of the epithelium. In contrast, contractile responses to acetylcholine were not altered by erythromycin. These results suggest that erythromycin may inhibit neuro-effector transmission in the airway cholinergic motor pathway, probably involving the reduction of exocytotic release of acetylcholine from the nerve terminals.