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1 Division of Pathology, Department of Pediatric Laboratory Medicine, The Research Institute, The Hospital for Sick Children and University of Toronto, Toronto, Ontario, Canada
2 Department of Biology, McMaster University, , Hamilton, Ontario, Canada
* To whom correspondence should be addressed. E-mail: ernest.cutz{at}sickkids.ca.
Pulmonary neuroepithelial bodies (NEB) are presumed airway chemoreceptors involved in respiratory control, especially in the neonate. Nicotine is known to affect both the lung development and control of breathing. We report expression of functional nicotinic acetylcholine receptors (nAChR) in NEB cells of neonatal hamster lung using a combination of morphologic and electrophysiological techniques. Non-isotopic in situ hybridization method was used to localize mRNA for
2 subunit of nAChR in NEB cells. Double label immunofluoresence confirmed expression of
4,
7 and
2 subunits of nAChR in NEB cells. The electrophysiological characteristics of nAChR in NEB cells were studied using whole-cell patch-clamp technique on fresh lung slices. Application of nicotine (0.1µM ~ 100µM) evoked inward currents that were concentration-dependent (EC50 = 3.8µM; Hill Coefficient = 1.1). Acetycholine (100µM) and nicotine (50µM) produced two types of currents. In most NEB cells, nicotine-induced currents had a single desensitizing component that was blocked by mecamylamine (50µM) and DH
E (50µM). In some NEB cells, nicotine-induced current had two components, with fast and slow desensitizing kinetics. The fast component was selectively blocked by methyllcaconitine (MLA, 10 nM), whereas both components were inhibited by mecamylamine. Choline (0.5 mM) also induced an inward current that was abolished by 10 nM MLA. These studies suggest that NEB cells in neonatal hamster lung express functional heteromeric
3
2,
4
2 and
7 nAChR and that cholinergic mechanisms could modulate NEB chemoreceptor function under normal and pathological conditions.
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