Malone H M, Peters J A, Lambert J J
Department of Pharmacology and Clinical Pharmacology, Ninewells Hospital and Medical School, University of Dundee.
Neuropeptides. 1991 Jul;19 Suppl:25-30. doi: 10.1016/0143-4179(91)90080-3.
Whole cell and patch clamp techniques were used to investigate the properties of 5-HT3 receptors of a murine neuroblastoma cell line (N1E-115) and adult rabbit nodose ganglion neurones. In addition, some preliminary results from guinea-pig nodose ganglion neurones are presented. In such cells, voltage-clamped at -60 mV, 5-HT (10 microM) induced an inward current associated with a conductance increase. The results of ion substitution experiments suggest that the 5-HT activated ion channel is permeable to both Na+ and K+ ions with a permeability ratio (PNa/PK) of 0.94 and 0.92 for rabbit nodose ganglion cells and N1E-115 cells respectively. On outside out membrane patches excised from rabbit nodose ganglion neurones, 5-HT (1 microM) activated clearly discernible single channel currents with a conductance of 16.6 +/- 0.7 pS (n = 4). In contrast, fluctuation analysis of 5-HT induced whole cell currents suggests that the single channel conductance of N1E-115 cells is only 0.3 pS, a value some 50 fold lower. The 5-HT-induced whole cell currents recorded from all three preparations were antagonised by the selective 5-HT3 receptor antagonist ondansetron (GR38032F) and by the less selective agents metoclopramide, cocaine and (+)-tubocurarine. However, these preparations demonstrate a differential sensitivity to some antagonists. In particular, (+)-tubocurarine was a potent antagonist in N1E-115 cells (IC50 = 0.85 nM) but was approximately 200 fold (IC50 = 156 nM) and 1200 fold (IC50 = 10 microM) less potent in rabbit and guinea-pig nodose ganglion neurones respectively. Additionally, a novel effect of ketamine (10 microM) to potentiate the 5-HT-induced current of rabbit nodose ganglion neurones is described.
采用全细胞和膜片钳技术研究了小鼠神经母细胞瘤细胞系（N1E-115）和成年兔结状神经节神经元5-HT3受体的特性。此外，还给出了豚鼠结状神经节神经元的一些初步结果。在这些细胞中，电压钳制在-60 mV时，5-HT（10 μM）诱导出与电导增加相关的内向电流。离子置换实验结果表明，5-HT激活的离子通道对Na+和K+离子均通透，兔结状神经节细胞和N1E-115细胞的通透率比（PNa/PK）分别为0.94和0.92。从兔结状神经节神经元上切下的外侧向外膜片上，5-HT（1 μM）激活了明显可辨的单通道电流，电导为16.6±0.7 pS（n = 4）。相比之下，对5-HT诱导的全细胞电流进行波动分析表明，N1E-115细胞的单通道电导仅为0.3 pS，该值低约50倍。从所有三种标本记录的5-HT诱导的全细胞电流均被选择性5-HT3受体拮抗剂昂丹司琼（GR38032F）以及选择性较低的药物甲氧氯普胺、可卡因和（+）-筒箭毒碱所拮抗。然而，这些标本对某些拮抗剂表现出不同的敏感性。特别是，（+）-筒箭毒碱在N1E-115细胞中是一种强效拮抗剂（IC50 = 0.85 nM），但在兔和豚鼠结状神经节神经元中效力分别低约200倍（IC50 = 156 nM）和1200倍（IC50 = 10 μM）。此外，还描述了氯胺酮（10 μM）增强兔结状神经节神经元5-HT诱导电流的新效应。
