Weaver W R, Chiappinelli V A
Department of Pharmacological and Physiological Science, St. Louis University School of Medicine, MO 63104, USA.
Brain Res. 1996 Jun 24;725(1):95-105. doi: 10.1016/0006-8993(96)00391-5.
We examined the functional properties of central nicotinic acetylcholine receptors at the single-channel level using tight-seal, voltage-clamp techniques. Single-channel currents were recorded from cell-attached patches on lateral spiriform neurons in chick brain slices. These neurons are known to express functional nicotinic receptors that are insensitive to the antagonists alpha-bungarotoxin and kappa-bungarotoxin, and which exhibit a high affinity for nicotine and other nicotinic agonists. Single-channel openings were observed in 84% of patches (n = 118) when the nicotinic agonists acetylcholine (1-100 microM), carbamylcholine (3-100 microM), or nicotine (3-10 microM) were present in the patch pipette. In contrast, single-channels were markedly reduced in number or entirely absent when the nicotinic antagonist dihydro-beta-erythroidine was present along with acetylcholine (n = 7) or when no agonist was present in the pipette (n = 22). Single-channel openings displayed inward rectification at depolarized potentials, and were dependent on extracellular sodium. Between 1 and 30 microM acetylcholine, a dose-response relationship was observed between agonist concentration and single-channel open probability during the first minute following seal formation. Multiple classes of single nicotinic channels, with calculated mean slope conductances of 15, 31, 40, and approximately 70 pS, were observed in membrane patches on different neurons within the lateral spiriform nucleus, and even within single patches on individual neurons. We conclude that neurons within the lateral spiriform nucleus express functionally heterogeneous nicotinic receptors and that in some neurons different nicotinic receptor subtypes are present in close proximity to each other on the same cell surface.
我们使用紧密封接电压钳技术在单通道水平研究了中枢烟碱型乙酰胆碱受体的功能特性。从鸡脑片外侧螺旋神经元的细胞贴附式膜片上记录单通道电流。已知这些神经元表达对拮抗剂α-银环蛇毒素和κ-银环蛇毒素不敏感、对尼古丁和其他烟碱型激动剂具有高亲和力的功能性烟碱型受体。当膜片吸管中存在烟碱型激动剂乙酰胆碱（1 - 100微摩尔）、氨甲酰胆碱（3 - 100微摩尔）或尼古丁（3 - 10微摩尔）时，在84%的膜片（n = 118）中观察到单通道开放。相比之下，当烟碱型拮抗剂二氢-β-刺桐啶与乙酰胆碱同时存在时（n = 7）或吸管中不存在激动剂时（n = 22），单通道数量明显减少或完全不存在。单通道开放在去极化电位下表现出内向整流，并且依赖于细胞外钠离子。在1至30微摩尔乙酰胆碱浓度范围内，在形成封接后的第一分钟内，观察到激动剂浓度与单通道开放概率之间存在剂量反应关系。在外侧螺旋状核内不同神经元的膜片上，甚至在单个神经元的单个膜片上，观察到了多类单烟碱型通道，计算得出的平均斜率电导分别为15、31、40和约70皮西门子。我们得出结论，外侧螺旋状核内的神经元表达功能异质性的烟碱型受体，并且在一些神经元中，不同的烟碱型受体亚型在同一细胞表面彼此紧邻存在。
