Adrenergic and cholinergic nerves mediate fluid secretion from tracheal glands of ferrets

Our aim was to determine whether adrenergic as well as cholinergic nerves mediate secretion of fluids from tracheal submucosal glands and, if so, via which receptors. To do this, we studied the secretory responses of tracheal segments to electrical and pharmacologic stimulation in vitro in the presence and absence of a specific nerve blocker and autonomic antagonists. Stimulation caused small elevations, or "hillocks," the size of which we estimated by measuring their diameters. We found that electrical stimulation, acetylcholine, and phenylephrine each caused secretion but that terbutaline did not. Tetrodotoxin prevented the secretory response to electrical stimulation but did not prevent the responses to acetylcholine or phenylephrine. Neither atropine nor phentolamine alone prevented the response to electrical stimulation, but both drugs together did, and propranolol did not inhibit the adrenergic component of the response to electrical stimulation. Atropine blocked the response to acetylcholine, and phentolamine blocked the response to phenylephrine. We conclude that adrenergic and cholinergic nerves mediate secretion from the tracheal glands of ferrets via alpha-adrenergic and muscarinic receptors, respectively.