大鼠视上核神经元胞体和轴突终末中不同的ω-芋螺毒素敏感钙电流。

Distinct omega-agatoxin-sensitive calcium currents in somata and axon terminals of rat supraoptic neurones.

Fisher T E, Bourque C W

Centre for Research in Neuroscience, McGill University, Montreal, Quebec, Canada.

J Physiol. 1995 Dec 1;489 ( Pt 2)(Pt 2):383-8. doi: 10.1113/jphysiol.1995.sp021059.

Abstract

Voltage-dependent calcium currents were measured at room temperature using whole-cell patch clamp in acutely isolated somata and axon terminals of the magnocellular neurosecretory cells (MNCs) from the rat supraoptic nucleus. 2. Administration of omega-agatoxin IVA (omega-Aga IVA) blocked a high-threshold non-inactivating current. This current has an IC50 for omega-Aga IVA of 3 nM; no other types of currents were blocked at doses of up to 500 nM. 3. In the axon terminals omega-Aga IVA blocked a high-threshold current that inactivates markedly (tau approximately 448 ms), and has a much lower sensitivity to the toxin, with an IC50 of 270 nM. Unlike the somatic current, the effect of omega-Aga IVA in the terminals is largely prevented by omega-conotoxin GVIA (omega-CgTX). 4. These data suggest that MNC somata express a single type of omega-Aga IVA-sensitive calcium current similar to the P-type calcium current described in other cells. However, the omega-Aga IVA-sensitive current in axon terminals differs from both the P-type and the recently identified Q-type current in that it is also sensitive to omega-CgTX. The distinct biophysical properties of the currents in somata and axon terminals may have important physiological implications.

摘要

在室温下，使用全细胞膜片钳技术在急性分离的大鼠视上核大细胞神经分泌细胞（MNCs）的胞体和轴突终末测量电压依赖性钙电流。2. 给予ω-芋螺毒素IVA（ω-Aga IVA）可阻断一种高阈值非失活电流。该电流对ω-Aga IVA的半数抑制浓度（IC50）为3 nM；在高达500 nM的剂量下，未阻断其他类型的电流。3. 在轴突终末，ω-Aga IVA阻断一种高阈值电流，该电流明显失活（时间常数约为448毫秒），并且对该毒素的敏感性低得多，IC50为270 nM。与胞体电流不同，ω-芋螺毒素GVIA（ω-CgTX）在很大程度上可阻止ω-Aga IVA在终末的作用。4. 这些数据表明，MNC胞体表达一种单一类型的对ω-Aga IVA敏感的钙电流，类似于其他细胞中描述的P型钙电流。然而，轴突终末中对ω-Aga IVA敏感的电流不同于P型电流和最近鉴定的Q型电流，因为它也对ω-CgTX敏感。胞体和轴突终末中电流独特的生物物理特性可能具有重要的生理学意义。