在离体大鼠脊髓中研究运动神经元膜电位对细胞外离子浓度的依赖性。
The dependence of motoneurone membrane potential on extracellular ion concentrations studied in isolated rat spinal cord.
作者信息
Forsythe I D, Redman S J
机构信息
Experimental Neurology Unit, John Curtin School of Medical Research, Australian National University, Canberra, A.C.T.
出版信息
J Physiol. 1988 Oct;404:83-99. doi: 10.1113/jphysiol.1988.sp017280.
Abstract
- Intracellular recordings from ninety-nine motoneurones have been made in an in vitro hemisected spinal cord preparation. Their mean resting membrane potential in normal artificial cerebrospinal fluid (CSF) was -71 +/- 0.5 mV (+/- S.E.M.). The mean amplitude of the action potential was 84.0 +/- 1.4 mV (n = 50), and the mean input conductance was 101 +/- 7 nS (n = 49). 2. Both membrane potential and input conductance were sensitive to changes in [K+]o, [Na+]o, [Cl-]o and [Ca2+]o. 3. Replacement of extracellular Ca2+ by Mn2+ resulted in less than 1 mV hyperpolarization and a decrease in input conductance from 102 +/- 7 to 93 +/- 6 nS (n = 15). 4. At high [K+]o (greater than 10 mM) the membrane potential followed the potential predicted by the Nernst equation for K+ ions with a slope of 58 mV per 10-fold change in [K+]o. At low [K+]o (less than 10 mM) there was significant deviation from K+ equilibrium potential (EK). 5. [K+]i was found to be 106 mM when estimated from the reversal potential of the after-hyperpolarization of the antidromic action potential. 6. The reversal potential of the recurrent inhibitory postsynaptic potential (IPSP) in normal CSF was used to calculate [Cl-]i. This was 6.6 mM, which is less than would be expected if Cl- was passively distributed, indicating the presence of an outwardly directed Cl- pump. 7. Decreasing [Cl-]o from control (134 mM) to 4 mM resulted in a depolarization of 6.9 +/- 0.9 mV and a decrease in input conductance from 102 +/- 5 to 90 +/- 5 nS (n = 14) in 3 mM [K+]o. 8. Decreasing [Na+]o from 156 to 26 mM by substitution with choline resulted in a 6.2 +/- 0.5 mV hyperpolarization and a decrease in input conductance from from 102 +/- 4 to 76 +/- 4 nS (n = 5) in 3 mM [K+]o. 9. The input conductances for Na+, Cl- and K+ at the resting potential were calculated. After allowing for a microelectrode leak conductance, the relative input conductances were gNa/gK = 0.13 and gCl/gK = 0.25.
摘要
- 在体外半切脊髓标本中，对99个运动神经元进行了细胞内记录。它们在正常人工脑脊液（CSF）中的平均静息膜电位为-71±0.5 mV（±标准误）。动作电位的平均幅度为84.0±1.4 mV（n = 50），平均输入电导为101±7 nS（n = 49）。2. 膜电位和输入电导对[K⁺]ₒ、[Na⁺]ₒ、[Cl⁻]ₒ和[Ca²⁺]ₒ的变化均敏感。3. 用Mn²⁺替代细胞外Ca²⁺导致超极化小于1 mV，输入电导从102±7 nS降至93±6 nS（n = 15）。4. 在高[K⁺]ₒ（大于10 mM）时，膜电位遵循能斯特方程预测的K⁺离子电位，斜率为每10倍[K⁺]ₒ变化58 mV。在低[K⁺]ₒ（小于10 mM）时，与K⁺平衡电位（EK）有显著偏差。5. 根据逆向动作电位后超极化的反转电位估计，[K⁺]i为106 mM。6. 正常CSF中，用回返性抑制性突触后电位（IPSP）的反转电位来计算[Cl⁻]i。其值为6.6 mM，低于Cl⁻被动分布时预期的值，表明存在外向的Cl⁻泵。7. 将[Cl⁻]ₒ从对照值（134 mM）降至4 mM，在3 mM [K⁺]ₒ时导致去极化6.9±0.9 mV，输入电导从102±5 nS降至90±5 nS（n = 14）。8. 用胆碱替代使[Na⁺]ₒ从156 mM降至26 mM，在3 mM [K⁺]ₒ时导致超极化6.2±0.5 mV，输入电导从102±4 nS降至76±4 nS（n = 5）。9. 计算了静息电位时Na⁺、Cl⁻和K⁺的输入电导。扣除微电极漏电导后，相对输入电导为gNa/gK = 0.13，gCl/gK = 0.25。
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