The role of GABAergic inputs for coincidence detection in the neurones of nucleus laminaris of the chick
The role of GABAergic inputs for coincidence detection in the neurones of nucleus laminaris of the chick
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DOI：
10.1111/j.1469-7793.1998.851bp.x
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发表时间：
1998-05-01
影响因子：
5.5
通讯作者：
Ohmori, H
中科院分区：
文献类型：
--
作者：
Funabiki, K;Koyano, K;Ohmori, H
1. 利用全细胞膜片钳技术，在鸡胚（E15-20）的脑干切片制备中研究了突触对层状核神经元的输入。NL神经元是一种三阶听觉神经元，被认为是与时间鉴别有关的巧合检测器。在电压箝位条件下，施加于树突腹侧或背侧的电刺激均可诱发epsc。这些快速电流在静息电位附近以1.1 ms的时间常数衰减，在0 mV附近反转，并被6-氰-7-硝基喹啉-2,3-二酮（CNQX, 20 μ M）或6,7-二硝基喹啉-2,3-二酮（DNQX, 20 μ M）阻断。同时或接近同时刺激腹侧和背侧树突层增加动作电位产生的概率（反应概率）。在CNQX （40 μ M）的存在下，观察到其他突触后电流（PSCs），其逆转接近氯离子（E-Cl）的平衡电位，并被双球茎碱（20 μ M）可逆阻断，因此由GABA受体介导。在低Cl- (5 mM, E-Cl = -90 mV)移液培养基中开始全细胞记录后，自发的GABAergic PSCs立即向内靠近静息膜电位，但随着时间的推移逐渐向外移动。这表明gaba能输入可能在完整的NL神经元中产生去极化电位。局部GABA （10 μ M）降低了EPSP和EPSC的振幅，缩短了EPSP的衰减时间常数（从5.3 ms降至1.2 ms），而EPSC的衰减时间常数不受影响（从1.3 ms降至1.2 ms）。这些GABA效应主要是由于突触后GABA受体的传导分流。去极化电流注射结合电刺激单侧轴突束模拟双侧突触输入。反应概率随着刺激间隔时间的缩短而增加，而局部GABA （10 μ M）作用于体细胞缩小了反应概率的时间依赖性。这些结果表明，NL神经元的gaba能输入可能通过增加膜电导来改善双侧兴奋性输入的一致性检测。
1. Synaptic inputs to nucleus laminaris (NL) neurones were studied in a brainstem slice preparation of chick embryos (E15-20) using the whole-cell patch clamp technique. NL neurones are third order auditory neurones and are proposed to behave as coincidence detectors concerned viith interaural timing discrimination.2. Under voltage clamp conditions, electrical stimuli applied to either ventral or dorsal dendritic layers evoked EPSCs. These fast currents decayed with a time constant of 1.1 ms near the resting potential, reversed close to 0 mV, and were blocked by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, 20 mu M) or 6,7-dinitro-quinoxaline-2,3-dione (DNQX, 20 mu M). Coincident or near coincident stimulation of the ventral and the dorsal dendritic layers increased the probability of action potential generation (response probability).3. Ln the presence of CNQX (40 mu M) other postsynaptic currents (PSCs) were observed, which reversed close to the equilibrium potential for chloride (E-Cl), and were reversibly blocked by bicuculline (20 mu M) and, therefore, were mediated by GABA, receptors. Spontaneous GABAergic PSCs were inward going near the resting membrane potential immediately after starting whole-cell recording with a low Cl- (5 mM, E-Cl = -90 mV) pipette medium, but became outward-going with time. This indicates that GABAergic inputs may generate depolarizing potentials in intact NL neurones.4. Local GABA (10 mu M) application reduced both the EPSP and EPSC amplitude and shortened the EPSP decay time constant (from 5.3 to 1.2 ms), while the EPSC decay time constant wets not affected (from 1.3 to 1.2 ms). These GABA effects were mostly due to the shunting conductance of the postsynaptic GABA, receptors.5. Depolarizing current injections combined with electrical stimuli to a unilateral axon bundle simulated bilateral synaptic inputs. Response probability increased with decreased interstimulus intervals, while local GABA (10 mu M) application to the soma narrowed the time dependence of the response probability.6. These results suggest that GABAergic inputs to NL neurones may serve to improve coincidence detection of the bilateral excitatory inputs through an increase in membrane conductance.