J. Tamaoki et al., CHOLINERGIC CONTROL OF RABBIT TRACHEAL TRANSEPITHELIAL POTENTIAL DIFFERENCE IN-VIVO, The European respiratory journal, 9(8), 1996, pp. 1632-1636
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.