培养的已鉴定水蛭神经元中的钠、钾和钙电流。

Na+, K+ and Ca2+ currents in identified leech neurones in culture.

作者信息

Stewart R R, Nicholls J G, Adams W B

机构信息

Biocenter, University of Basel, Switzerland.

出版信息

J Exp Biol. 1989 Jan;141:1-20. doi: 10.1242/jeb.141.1.1.

DOI:10.1242/jeb.141.1.1

PMID:2538540

Abstract

Na+, K+ and Ca2+ currents have been measured by voltage-clamp in Retzius (R), anterior pagoda (AP) and sensory (pressure, touch and nociceptive) cells dissected from the central nervous system (CNS) of the leech. These cells maintain their distinctive membrane properties and action potential configurations in culture. Currents carried by the individual ions were analysed by the use of channel blockers and by their kinetics. Since the cells are isopotential they can be voltage-clamped effectively. 2. Depolarization, as expected, gave rise to an early inward Na+ current followed by a delayed outward K+ current. In Na+-free medium containing tetraethylammonium (TEA+), and in the presence of 4-aminopyridine (4-AP), inward Ca2+ currents were revealed that inactivated slowly and were blocked by Cd2+ and Mn2+. 3. Na+ and Ca2+ currents were similar in their characteristics in R. AP and sensory neurones. In contrast, K+ currents showed marked differences. Three principal K+ currents were identified. These differed in their time courses of activation and inactivation and in their responses to Ca2+ channel blockers. 4. K+ currents of the A-type (IA) activated and inactivated rapidly, were not affected by Ca2+ channel blockers and were eliminated by steady-state inactivation at holding potentials of -30 mV. A-type K+ currents were found in AP cells and as a minor component of the outward current in R cells. A Ca2+-activated K+ current (IC), that inactivated more slowly and was reduced by Ca2+ channel blockers, constituted the major outward current in R cells. The third K+ current resembled the delayed rectifier currents (IK1 and IK2) of squid axons with slow activation and inactivation kinetics. Such currents were found in R cells and in the sensory neurones (T, P and N). 5. The principal differences in membrane properties of identified leech neurones can be explained in terms of the numbers of Na+ channels and the distinctive kinetics of K+ channels in each type of cell.

摘要

利用电压钳技术测量了从水蛭中枢神经系统（CNS）分离出的雷丘斯（R）细胞、前塔（AP）细胞和感觉（压力、触觉和伤害性感受）细胞中的钠离子（Na⁺）、钾离子（K⁺）和钙离子（Ca²⁺）电流。这些细胞在培养过程中保持其独特的膜特性和动作电位形态。通过使用通道阻滞剂及其动力学特性来分析单个离子所携带的电流。由于这些细胞是等电位的，因此可以有效地进行电压钳制。2. 正如预期的那样，去极化引发了早期内向Na⁺电流，随后是延迟外向K⁺电流。在含有四乙铵（TEA⁺）的无钠培养基中，以及在4-氨基吡啶（4-AP）存在的情况下，揭示了内向Ca²⁺电流，其失活缓慢，并被Cd²⁺和Mn²⁺阻断。3. Na⁺和Ca²⁺电流在R细胞、AP细胞和感觉神经元中的特性相似。相比之下，K⁺电流表现出明显差异。确定了三种主要的K⁺电流。它们在激活和失活的时间进程以及对Ca²⁺通道阻滞剂的反应方面有所不同。4. A型K⁺电流（IA）快速激活和失活，不受Ca²⁺通道阻滞剂影响，并在-30 mV的钳制电位下通过稳态失活而消除。在AP细胞中发现了A型K⁺电流，并且是R细胞外向电流的次要成分。一种Ca²⁺激活的K⁺电流（IC），其失活较慢且被Ca²⁺通道阻滞剂减弱，构成了R细胞中的主要外向电流。第三种K⁺电流类似于鱿鱼轴突的延迟整流电流（IK1和IK2），具有缓慢的激活和失活动力学。在R细胞和感觉神经元（T、P和N）中发现了这种电流。5. 已确定的水蛭神经元膜特性的主要差异可以根据每种细胞类型中Na⁺通道的数量以及K⁺通道独特的动力学特性来解释。