Fu Xiao Wen, Nurse Colin A, Farragher Suzanne M, Cutz Ernest
Division of Pathology, Department of Pediatric Laboratory Medicine, Hospital for Sick Children, 555 Univ. Ave., Toronto, Ontario, Canada M5G 1X8.
Am J Physiol Lung Cell Mol Physiol. 2003 Dec;285(6):L1203-12. doi: 10.1152/ajplung.00105.2003. Epub 2003 Jun 20.
Pulmonary neuroepithelial bodies (NEB) are presumed airway chemoreceptors involved in respiratory control, especially in the neonate. Nicotine is known to affect both 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 morphological and electrophysiological techniques. Nonisotopic in situ hybridization method was used to localize mRNA for the beta 2-subunit of nAChR in NEB cells. Double-label immunofluorescence confirmed expression of alpha 4-, alpha 7-, and beta 2-subunits of nAChR in NEB cells. The electrophysiological characteristics of nAChR in NEB cells were studied using the whole cell patch-clamp technique on fresh lung slices. Application of nicotine ( approximately 0.1-100 microM) evoked inward currents that were concentration dependent (EC50 = 3.8 microM; Hill coefficient = 1.1). ACh (100 microM) and nicotine (50 microM) produced two types of currents. In most NEB cells, nicotine-induced currents had a single desensitizing component that was blocked by mecamylamine (50 microM) and dihydro-beta-erythroidine (50 microM). 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 alpha 3 beta 2, alpha 4 beta 2, and alpha 7 nAChR and that cholinergic mechanisms could modulate NEB chemoreceptor function under normal and pathological conditions.
肺神经上皮小体（NEB）被认为是参与呼吸控制的气道化学感受器，尤其是在新生儿中。已知尼古丁会影响肺发育和呼吸控制。我们使用形态学和电生理学技术相结合的方法，报告了新生仓鼠肺NEB细胞中功能性烟碱型乙酰胆碱受体（nAChR）的表达。采用非同位素原位杂交方法在NEB细胞中定位nAChRβ2亚基的mRNA。双标记免疫荧光证实了NEB细胞中nAChR的α4、α7和β2亚基的表达。使用新鲜肺切片上的全细胞膜片钳技术研究了NEB细胞中nAChR的电生理特性。应用尼古丁（约0.1 - 100μM）可诱发内向电流，该电流呈浓度依赖性（EC50 = 3.8μM；希尔系数 = 1.1）。乙酰胆碱（100μM）和尼古丁（50μM）产生两种类型的电流。在大多数NEB细胞中，尼古丁诱导的电流具有单一脱敏成分，该成分被美加明（50μM）和二氢β - 刺桐啶（50μM）阻断。在一些NEB细胞中，尼古丁诱导的电流有两个成分，具有快速和缓慢脱敏动力学。快速成分被甲基乌头碱（MLA，10 nM）选择性阻断，而两个成分均被美加明抑制。胆碱（0.5 mM）也诱导了一种内向电流，该电流被10 nM MLA消除。这些研究表明，新生仓鼠肺中的NEB细胞表达功能性异聚体α3β2、α4β2和α7 nAChR，并且胆碱能机制可能在正常和病理条件下调节NEB化学感受器功能。
