Subthreshold membrane resonance in neocortical neurons
Subthreshold membrane resonance in neocortical neurons
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DOI：
10.1152/jn.1996.76.2.683
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发表时间：
1996-08-01
影响因子：
2.5
通讯作者：
Puil, E
中科院分区：
文献类型：
--
作者：
Hutcheon, B;Miura, RM;Puil, E
1.采用全细胞记录技术，研究了幼年大鼠感觉运动皮层神经元对振荡电流输入的阈下和阈上电压反应.根据放电模式，神经元被分为规则发放（RS），内在爆发（IB）和快速发放（FS）。RS和IB神经元的阈下电压-电流关系为整流型，而FS神经元的阈下电压-电流关系接近于欧姆型.神经元的频率响应曲线（FRC）通过分析输入和输出的频率内容来确定。大多数神经元的FRC在低于但不高于20 Hz的频率下具有电压依赖性。大约60%的RS和IB神经元在其静息电位下具有膜共振。共振频率在0.7和2.5 Hz（24-26 ℃）之间，接近-70 mV，通常随超极化而增加，随去极化而降低。其余RS和IB神经元以及所有FS神经元均为非共振.共振神经元接近休息时，振荡输入和放电之间有一个选择性耦合。这些神经元选择性地发射动作电位时，扫频正弦波（ZAP）电流输入的频率接近共振频率。然而，当这些神经元被去极化到-60 mV时，锋电位放电与许多输入频率相关，而不是选择性地接近共振频率.我们研究了三种可能引起低频共振的阈下电流：I-H，一种缓慢的、超极化激活的阳离子电流，可被外部Cs+阻断，但不被Ba 2+阻断; I-IR，一种瞬时激活的、内向整流的K+电流，可被Cs+和Ba 2+阻断; I-NaF，一种快速激活的、内向整流的持续性Na+电流，可被河豚毒素（TTX）阻断。电压钳实验定义了这些电流的相对稳态激活范围。I-IR（低于-80 mV激活）和I-NaP（高于-65 mV激活）不太可能相互作用，因为它们的激活范围从不重叠。然而，这两种电流都可以与I相互作用，I在不同神经元中在-50 mV和-90 mV之间的电位下激活I。我们发现IH产生阈下共振。与此一致，阈下共振被外部Cs+阻断，但不被Ba 2+或TTX阻断。Ba 2+的应用在低于-80 mV的电位下放大了FRC和共振，表明I-K，I-ir通常会衰减共振。TTX的应用大大减弱了在比-65 mV更去极化的电位下的共振，表明I-NaP通常在这些电位下放大共振。ZAP电流输入可以被视为在大脑中的同步活动期间在新皮层神经元中出现的振荡电流的模型。我们建议，频率选择性赋予神经元的IH可能有助于他们参与同步放电。振荡输入和尖峰之间的频率选择性耦合的电压依赖性可能指示用于控制新皮层中的低频同步活动的程度的新机制。
1. Using whole cell recording techniques, we studied subthreshold and suprathreshold voltage responses to oscillatory current inputs in neurons from the sensorimotor cortex of juvenile rats.2. Based on firing patterns, neurons were classified as regular spiking (RS), intrinsic bursting (IB), and fast spiking (FS). The subthreshold voltage-current relationships of RS and IB neurons were rectifying whereas FS neurons were almost ohmic near rest.3. Frequency response curves (FRCs) for neurons were determined by analyzing the frequency content of inputs and outputs. The FRCs of most neurons were voltage dependent at frequencies below, but not above, 20 Hz. Approximately 60% of RS and IB neurons had a membrane resonance at their resting potential. Resonant frequencies were between 0.7 and 2.5 Hz (24-26 degrees C) near -70 mV and usually increased with hyperpolarization and decreased with depolarization. The remaining RS and IB neurons and all FS neurons were nonresonant.4. Resonant neurons near rest had a selective coupling between oscillatory inputs and firing. These neurons selectively fired action potentials when the frequency of the swept-sine-wave (ZAP) current input was near the resonant frequency. However, when these neurons were depolarized to -60 mV, spike firing was associated with many input frequencies rather than selectively near the resonant frequency.5. We examined three subthreshold currents that could cause low frequency resonance: I-H, a slow, hyperpolarization-activated cation current that was blocked by external Cs+ but not Ba2+; I-IR, an instantaneously activating, inwardly rectifying K+ current that was blocked by both Cs+ and Ba2+; and I-NaF, an quickly activating, inwardly rectifying persistent Na+ current that was blocked by tetrodotoxin (TTX). Voltage-clamp experiments defined the relative steady state activation ranges of these currents. I-IR (activates below -80 mV) and I-NaP(activates above -65 mV) are unlikely to interact with each other because their activation ranges never overlap. However, both currents may interact with I,, which activated variably at potentials between -50 and -90 mV in different neurons.6. We found that IH produces subthreshold resonance. Consistent with this, subthreshold resonance was blocked by external Cs+ but not Ba2+ or TTX. Application of Ba2+ enlarged FRCs and resonance at potentials below -80 mV, indicating that I-K,I-ir normally attenuates resonance. Application of TTX greatly diminished resonance at potentials more depolarized than -65 mV, indicating that I-NaP normally amplifies resonance at these potentials.7. The ZAP current input may be viewed as a model of oscillatory currents that arise in neocortical neurons during synchronized activity in the brain. We propose that the frequency selectivity endowed on neurons by IH may contribute to their participation in synchronized firing. The voltage dependence of the frequency selective coupling between oscillatory inputs and spikes may indicate a novel mechanism for controlling the extent of low-frequency synchronized activity in the neocortex.