The effect of epithelium removal on non-adrenergic, non-cholinergic inhibitory responses in the isolated central airways of the cat and guinea pig.

Epithelium removal from the feline or the indomethacin-treated guinea pig trachea had no effect on tissue sensitivity or responsiveness to the contractile actions of pharmacological agonists or electrical field stimulation. In the feline hilar bronchus, epithelium removal had no effect on tissue sensitivity or responsiveness to acetylcholine or electrical field stimulation but increased bronchial sensitivity to serotonin without affecting responsiveness. Non-adrenergic non-cholinergic (NANC) relaxation responses elicited by electrical field stimulation in airway preparations from either species were unaffected by epithelium removal. These results suggest that the epithelium does not modulate contractile responses in the feline trachea but may modulate the actions of specific contractile agonists in the feline hilar bronchus. Further, NANC relaxation responses appear to occur independently of the airway epithelium.