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大鼠丘脑后外侧核神经元中的两种低电压激活钙通道。

Two types of low-voltage-activated Ca2+ channels in neurones of rat laterodorsal thalamic nucleus.

作者信息

Tarasenko A N, Kostyuk P G, Eremin A V, Isaev D S

机构信息

Department of General Physiology of Nervous System, Bogomoletz Institute of Physiology, National Academy of Sciences, Kiev-24, Ukraine.

出版信息

J Physiol. 1997 Feb 15;499 ( Pt 1)(Pt 1):77-86. doi: 10.1113/jphysiol.1997.sp021912.

Abstract
  1. The pharmacological and kinetic properties of two types of low-voltage-activated (LVA) Ca2+ currents were studied in thalamocortical neurones of the laterodorsal (LD) thalamic nucleus during early postnatal development. The whole-cell patch-clamp technique was used on brain slices from rats of three age groups: 12, 14 and 17 days old (postnatal day (P) 12, P14 and P17). 2. In P12 neurones, the population of LVA Ca2+ channels was homogeneous. LVA Ca2+ current elicited by depolarizing voltage steps from a holding potential more negative than -70 mV was sensitive to nifedipine (Kd = 2.6 microM). This current reached a maximum at about -55 mV and had a fast monoexponential decay with a time constant, tau h,f, of 32.3 +/- 4.0 ms. 3. The population of LVA Ca2+ channels in P14 and P17 neurones was found to be heterogeneous. A subpopulation of nifedipine-insensitive LVA Ca2+ channels was observed. The current-voltage curve of the Ca2+ current had a characteristic hump with two peaks at about -65 and -55 mV. As well as the fast component (designated IT,f), the decay of the LVA current also included a slow component (designated IT,s), with inactivation time constants (tau h,s) of 54.2 +/- 4.5 and 68.6 +/- 3.17 ms for P14 and P17 neurones, respectively. 4. The kinetics of both components could be well approximated by the m2h Hodgkin-Huxley equation. No significant difference in activation kinetics was observed. The activation time constants for the fast (tau m,f) and slow (tau m,s) components were 6.3 +/- 1.0 and 7.3 +/- 1.5 ms, respectively. 5. La3+ at a concentration of 1 microM effectively blocked the IT,f component but Ni2+ (25 microM) completely eliminated the IT,s component. 6. Steady-state inactivation curves of both components could be best fitted by a Boltzmann function with membrane potential values at half-maximal inactivation of -85.5 and -98.1 mV for the fast and slow components, respectively. 7. It was concluded that two different subtypes of LVA Ca2+ channel are present in LD neurones. Only the fast type is well expressed at the earliest postnatal stage (P12). The slow type could be found at the end of the second week (P14). The amplitude of the slow current increased progressively up to P17, obviously coinciding with dendritic expansion as judged by progressive increase of the membrane capacitance of the corresponding neurones. This property appears to differentiate neurones of the associative nuclei from neurones of other thalamic nuclei.
摘要
  1. 在出生后早期发育阶段,研究了外侧背核(LD)丘脑皮质神经元中两种类型的低电压激活(LVA)Ca2+电流的药理学和动力学特性。对三个年龄组大鼠(出生后第12天、第14天和第17天,即P12、P14和P17)的脑片使用全细胞膜片钳技术。2. 在P12神经元中,LVA Ca2+通道群体是同质的。从比 -70 mV更负的 holding 电位进行去极化电压阶跃引发的LVA Ca2+电流对硝苯地平敏感(Kd = 2.6 microM)。该电流在约 -55 mV时达到最大值,具有快速单指数衰减,时间常数tau h,f为32.3 +/- 4.0 ms。3. 发现P14和P17神经元中的LVA Ca2+通道群体是异质的。观察到一个对硝苯地平不敏感的LVA Ca2+通道亚群。Ca2+电流的电流 - 电压曲线有一个特征性的驼峰,在约 -65和 -55 mV处有两个峰值。除了快速成分(称为IT,f)外,LVA电流的衰减还包括一个缓慢成分(称为IT,s),P14和P17神经元的失活时间常数(tau h,s)分别为54.2 +/- 4.5和68.6 +/- 3.17 ms。4. 两个成分的动力学都可以很好地用m2h霍奇金 - 赫胥黎方程近似。在激活动力学方面未观察到显著差异。快速(tau m,f)和缓慢(tau m,s)成分的激活时间常数分别为6.3 +/- 1.0和7.3 +/- 1.5 ms。5. 1 microM浓度的La3+有效阻断IT,f成分,但25 microM的Ni2+完全消除IT,s成分。6. 两个成分的稳态失活曲线都可以最好地用玻尔兹曼函数拟合,快速和缓慢成分在半最大失活时的膜电位值分别为 -85.5和 -98.1 mV。7. 得出结论,LD神经元中存在两种不同亚型的LVA Ca2+通道。只有快速型在出生后最早阶段(P12)表达良好。缓慢型在第二周结束时(P14)可以发现。缓慢电流的幅度在P17之前逐渐增加,明显与相应神经元的膜电容逐渐增加所判断的树突扩展相一致。这种特性似乎将联合核的神经元与其他丘脑核的神经元区分开来。

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