ERYTHROMYCIN INHIBITS CHOLINERGIC NEUROEFFECTOR TRANSMISSION IN CANINE AIRWAY SMOOTH-MUSCLE

To elucidate whether macrolide antibiotics affect cholinergic neuro-ef fector transmission in the airway, we studied canine isolated bronchia l segments under isometric conditions in vitro. Addition of erythromyc in (3 x 10(-4) M) attenuated the contractile responses to electrical f ield stimulation (EFS), so that the stimulus frequency required to pro duce 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 an d not influenced by propranolol, indomethacin, ouabain or mechanical r emoval of the epithelium. In contrast, contractile responses to acetyl choline were not altered by erythromycin. These results suggest that e rythromycin may inhibit neuro-effector transmission in the airway chol inergic motor pathway, probably involving the reduction of exocytotic release of acetylcholine from the nerve terminals.