AIRWAY EPITHELIAL-CELLS MODULATE CHOLINERGIC NEUROTRANSMISSION IN DOGTRACHEA

We investigated the effects of epithelial cells on excitatory choliner gic neurotransmission in dog trachea, to shed more light on the role o f airway epithelial cells in regulating airway responsiveness. Airway epithelial cells were prepared by an enzymatic dissociation of the tra cheal mucosa using protease-free collagenase. Tracheal smooth muscle c ontractions evoked by electrical field stimulation (EFS) or acetylchol ine (ACh) were measured before and after the application of epithelial cells. Isolated and dispersed epithelial cells (3 x 10(5) cells/ml) s uppressed the amplitude of the twitch-like contractions evoked by EFS in the combined presence of guanethidine sulfate (10(-6) M) and indome thacin (10(-5) M). In contrast, epithelial cells did not affect the co ntraction evoked by exogenously applied ACh. Atropine (10(-6) M) or te trodotoxin (10(-7) M) abolished the contraction evoked by electrical f ield stimulation. These findings indicate that airway epithelial cells inhibit the excitatory neurotransmission of the vagus nerve, presumab ly by suppressing the release of ACh. Airway epithelial cells may ther efore play an important role in regulating the response of smooth musc le.