CHOLINERGIC CONTROL OF RABBIT TRACHEAL TRANSEPITHELIAL POTENTIAL DIFFERENCE IN-VIVO

The aim of the present study was to investigate the role of the autono mic nervous system in the regulation of airway epithelial ion transpor t in vivo. Rabbits were anaesthetized and mechanically-ventilated thro ugh a cannula inserted above the carina, The upper tracheal mucosa was exposed, and the electrical potential difference (PD) between the muc osal surface and the submucosal space was continuously measured by a h igh-impedance voltmeter under open-circuit conditions. Perfusion of th e mucosa with atropine caused a rapid decline in PD from -20.1+/-2.0 t o -15.2+/-0.9 mV (p<0.01), whereas phentolamine, propranolol, or the t achykinin antagonist, FK224, had no effect, Cuffing both cervical vagu s nerves decreased PD to the same degree as did atropine. Exogenously applied acetylcholine increased PD in a dose-dependent manner, Topical application of ipratropium bromide reduced the baseline value PD in a dose-dependent manner, The maximal decrease in PD was 4.3+/-0.3 mV (p <0.01), and the dose required to produce a half-maximal effect was 34 mu g. Perfusion with either amiloride, a Na channel blocker, and diphe nylamine-2-carboxylate, a Cl channel blocker, decreased the baseline P D, and the subsequent application of ipratropium bromide further decre ased the PD in each case. We conclude that a cholinergic neural compon ent may play a role in the generation of tracheal potential difference in vivo, probably involving stimulation by endogenously released acet ylcholine of both Cl secretion and Na absorption across the airway epi thelium.