CHARACTERIZATION OF SINGLE VOLTAGE-GATED NA+ AND CA2+ CHANNELS IN APICAL DENDRITES OF RAT CA1 PYRAMIDAL NEURONS
CHARACTERIZATION OF SINGLE VOLTAGE-GATED NA+ AND CA2+ CHANNELS IN APICAL DENDRITES OF RAT CA1 PYRAMIDAL NEURONS
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DOI：
10.1113/jphysiol.1995.sp020862
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发表时间：
1995-08-15
影响因子：
5.5
通讯作者：
JOHNSTON, D
中科院分区：
文献类型：
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作者：
MAGEE, JC;JOHNSTON, D
1.我们用树突连接膜片钳技术记录了CA1顶端树突(距胞体350微米)的单个Na~+和Ca~(2+)通道活动。1.大鼠海马片锥体神经元(年龄2-8周)。在所检查的每个贴片中都发现了NA+通道(范围：每个贴片2到20个通道)。斜率电导为15+/-0.3ps(平均值+/-S.E.M.)的通道开放以测试指令开始，达到-50 mV左右，包括早期的瞬时通道活动和后来发生的5-15ms的长时间开放。在记录吸管中加入河豚毒素(1mM)可抑制所有Na+通道的活动。在检查的斑块中，大约80%的斑块记录到了钙离子通道活动(范围：每个斑片1到10个通道)。在这些斑块中观察到了几种类型的通道行为。在110 mm BaCl2中的单通道记录显示，约有10ps通道的小单位电流幅度(-0.5pA，-20 mV)。这些通道在相对超极化的电位(-50 mV)下开始激活，而这种低电压激活(LVA)通道活动的整体平均值显示出快速失活。也遇到了高电压激活、中等电导(HVA(M)；大约17ps)、钙离子通道活动的有点不同的群体。这些通道表现出相对较大的单一幅度(在0 mV时为-0.8pA)，总体平均表现为中等失活。可以根据平均通道开放时间将通道的HVA_1种群暂时细分为两个单独的组。HVA、大电导(27pS)钙通道活动(HVA)也较少见。这种大的单一幅度(在0 mV时为-1.5pA)通道活动从阶跃到大约0 mV开始，总体平均值没有显示出任何依赖于时间的失活。二氢吡啶钙通道激动剂Bay K 8644(0.5或1亩M)被发现显著延长这些通道的开放。欧米茄-芋螺毒素MVIIC(10 MU M)并不显著减少树突状斑块中LVA、HVA或HVA通道类型记录到的通道活动量。在体节斑块中，6.W-芋螺毒素MVIIC能有效地消除大量的HVA(M)钙通道活动。在记录溶液中加入50或100亩M NiCl2显著减少了从树突斑块中的LVA和HVA记录的通道活动量。然而，HVA通道的一个亚群被发现对Ni2+不敏感。这些低浓度的Ni2+对树突状HVA的通道活性没有影响。阿米洛利(1 MM)显著降低LVA和HVA记录的通道活动，这两种通道位于树突状斑块。在成年动物的树突斑块中发现了相当恒定的密度，约有9个Na+通道和5个Ca+通道。树突状钙通道分布的基本轮廓为：HVA通道相对局限于近50微米，而LVA和HVA通道沿树突长度分布的频率相近。在CA1区锥体神经元顶端树突中发现一种单一类型的TTX敏感的Na+通道和至少三种不同类型的钙通道。三种主要类型的树突状钙通道呈现出与T-、R-和L型钙通道最为相似的特征。第四种钙通道的密度也较低，其特征与N型相似。
1. We have used dendrite-attached patch-clamp techniques to record single Na+ and Ca2+ channel activity from the apical dendrites (up to 350 mu m away from soma) of CA1. pyramidal neurons in rat hippocampal slices (ages: 2-8 weeks).2. Na+ channels were found in every patch examined (range: 2 to >20 channels per patch). Channel openings, which had a slope conductance of 15 +/- 0.3 pS (mean +/- S.E.M.), began with test commands to around -50 mV and consisted of both early transient channel activity and also later occurring prolonged openings of 5-15 ms. All Na+ channel activity was suppressed by inclusion of TTX (1 mu M) in the recording pipette.3. Ca2+ channel activity was recorded in about 80% of the patches examined (range: 1 to >10 channels per patch). Several types of channel behaviour were observed in these patches. Single channel recordings in 110 mM BaCl2, revealed an approximately 10 pS channel of small unitary current amplitude (-0.5 pA at -20 mV). These channels began activating at relatively hyperpolarized potentials (-50 mV) and ensemble averages of this low voltage-activated (LVA) channel activity showed rapid inactivation.4. A somewhat heterogeneous population of high voltage-activated, moderate conductance (HVA(m); approximately 17 pS), Ca2+ channel activity was also encountered. These channels exhibited a relatively large unitary amplitude (-0.8 pA at 0 mV) and ensemble averages demonstrated moderate inactivation. The HVA, population of channels could be tentatively subdivided into two separate groups based upon mean channel open times.5. Less frequently, HVA, large conductance (27 pS) Ca2+ channel activity (HVA,) was also observed. This large unitary amplitude (-1.5 pA at 0 mV) channel activity began with steps to approximately 0 mV and ensemble averages did not show any time-dependent inactivation. The dihydropyridine Ca2+ channel agonist Bay K 8644 (0.5 or 1 mu M) was found to characteristically prolong these channel openings. omega-Conotoxin MVIIC (10 mu M), did not significantly reduce the amount of channel activity recorded from the LVA, HVA, or HVA, channel types in dendritic patches. In patches from somata,6. w-conotoxin MVIIC was effective in eliminating a significant amount of HVA(m) Ca2+ channel activity. Inclusion of 50 or 100 mu M NiCl2 to the recording solution significantly reduced the amount of channel activity recorded from LVA and HVA, channel types in dendritic patches. A subpopulation of HVA, channels was, however, found to be Ni2+ insensitive. Dendritic HVA, channel activity was unaffected by these low concentrations of Ni2+. Amiloride (1 mM) substantially reduced channel activity recorded from LVA and HVA, channels located in dendritic patches.7. A fairly constant density of about nine Na+ and five Ca2+ channels was found in dendritic patches from adult animals. The basic profile for dendritic Ca2+ channel distribution was as follows: HVA, channels were relatively restricted to the proximal 50 mu m, while LVA and HVA, channels were found with similar frequency along the length of dendrite studied.8. A single type of TTX-sensitive Na+ channel and at least three distinct types of Ca2+ channel were found at substantial densities in the apical dendrites of CA1 pyramidal neurons. The three main types of dendritic Ca2+ channel presented characteristics most similar to T-, R- and L-type Ca2+ channels. A fourth type of Ca2+ channel, with characteristics similar to the N-type, was also found at a lower density.