Fractional Ca2+ currents through somatic and dendritic glutamate receptor channels of rat hippocampal CA1 pyramidal neurones
Fractional Ca2+ currents through somatic and dendritic glutamate receptor channels of rat hippocampal CA1 pyramidal neurones
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DOI：
10.1113/jphysiol.1996.sp021255
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发表时间：
1996-03-15
影响因子：
5.5
通讯作者：
Konnerth, A
中科院分区：
文献类型：
--
作者：
Garaschuk, O;Schneggenburger, R;Konnerth, A
1. 采用荧光通量测量法研究了大鼠海马CA1锥体神经元体和树突中非NMDA和NMDA受体通道的Ca2+通透性。为此，总阳离子电流的Ca2+分数（称为“分数Ca2+电流”）直接从Ca2+敏感fura-2荧光在380 nm激发波长的变化测量。通过体细胞NMDA受体通道的Ca2+电流分数为10.69 +/- 2.13%（平均+/- sd），通过树突受体通道的Ca2+电流分数为10.70 +/- 1.96%。分数Ca2+电流不依赖于细胞外Mg2+浓度，其电压依赖性与goldmanhodgkin - katz电流方程一致。AMPA （α -氨基-3-羟基-5-甲基异恶唑-4-丙酸盐）或kainate应用产生少量但显著的Ca2+进入。体细胞AMPA应用的分数Ca2+电流为0.58 +/- 0.34%，体细胞kainate应用的分数Ca2+电流为0.68 +/- 0.20%，树突AMPA应用的分数Ca2+电流为0.66 +/- 0.25%，树突kainate应用的分数Ca2+电流为0.61 +/- 0.16%。应用单细胞逆转录聚合酶链式反应（RT-PCR）方法分析了编码信使核糖核酸（mrna）的谷氨酸受体亚基在CA1锥体神经元中的表达模式。AMPA受体亚基GluR-A、GluR-B、GluR-C和NMDA受体亚基NR2A、NR2B丰富；在所有CA1锥体神经元中表达。本研究在CA1锥体神经元中建立了通过体细胞和树突NMDA和非NMDA受体通道的分数Ca2+电流。树突（可能是突触）的NMDA受体通道具有高度的Ca2+可渗透性，并且具有与体细胞突触外NMDA受体通道非常相似的分数Ca2+电流。体细胞和树突非NMDA受体通道都是“低Ca2+渗透性”类型，并且具有比NMDA受体通道小约20倍的分数Ca2+电流。
1. The Ca2+ permeability of non-NMDA and NMDA receptor channels was studied using a fluorometric flux measurement approach in somata and dendrites of CA1 pyramidal neurones in rat hippocampal slices. For this purpose, the Ca2+ fraction of the total cation current (named 'fractional Ca2+ current') was measured directly from the change in the Ca2+ sensitive fura-2 fluorescence at 380 nm excitation wavelength.2. The fractional Ca2+ current through the somatic NMDA receptor channels was 10.69 +/- 2.13% (mean +/- S.D.) and that through dendritic receptor channels was 10.70 +/- 1.96%. The fractional Ca2+ current was not dependent on the extracellular Mg2+ concentration and its voltage dependence was in agreement with the Goldman-Hodgkin-Katz current equation.3. AMPA (alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate) or kainate applications produced small but significant Ca2+ entry. Fractional Ca2+ currents of 0.58 +/- 0.34% were measured for somatic AMPA applications, 0.68 +/- 0.20% for somatic kainate applications, 0.66 +/- 0.25% for dendritic AMPA applications and 0.61 +/- 0.16% for dendritic kainate applications.4. The expression pattern of glutamate receptor subunits encoding messenger ribonucleic acids (mRNAs) was analysed with the single-cell reverse transcriptase-polymerase chain reaction (RT-PCR) approach applied to CA1 pyramidal neurones. The AMPA receptor subunits GluR-A, GluR-B and GluR-C, and the NMDA receptor subunits NR2A and NR2B were found to be abundantl;yr expressed in all CA1 pyramidal neurones tested.5. This study establishes the fractional Ca2+ current through somatic and dendritic NMDA and non-NMDA receptor channels in CA1 pyramidal neurones. The dendritic, presumably synaptic, NMDA receptor channels are highly Ca2+ permeable and have a fractional Ca2+ current closely resembling that of somatic extrasynaptic NMDA receptor channels. Both somatic and dendritic non-NMDA receptor channels are of the 'low Ca2+ permeable' type and have a fractional Ca2+ current that is about twenty times smaller than that of NMDA receptor channels.