Passive membrane properties and electrotonic signal processing in retinal rod bipolar cells
Passive membrane properties and electrotonic signal processing in retinal rod bipolar cells
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DOI：
10.1113/jphysiol.2008.165415
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发表时间：
2009-02-15
影响因子：
5.5
通讯作者：
Hartveit, Espen
中科院分区：
文献类型：
--
作者：
Oltedal, Leif;Veruki, Margaret Lin;Hartveit, Espen
视杆双极细胞将视觉信号从其树突传递到其轴突末端，在树突处视杆双极细胞接收来自视杆光感受器的输入，在轴突末端处视杆双极细胞与无长突细胞突触。然而，人们对这些信号的传输和可能的转换知之甚少。我们结合轴突终末记录在视网膜切片，定量，光学显微镜形态重建和计算机建模，以获得详细的大鼠杆双极细胞的房室模型。无源电缆性能估计直接拟合的电流响应的模型诱发的电压脉冲的生理记录的响应。在保持电位为-60 mV时，平均最佳拟合参数为：比膜电容（Cm）为1.1 μ F cm（-2），细胞质电阻率（Ri）为130 Ω cm（-2），比膜电阻（Rm）为24 k Ω cm（-2）。被动整合的兴奋性和抑制性突触输入进行了检查，通过计算机建模与生理现实的突触电导波形。对于瞬时和稳态突触抑制，抑制效应对抑制的位置相对不敏感。对于短暂的突触抑制，有效抑制的时间窗主要取决于抑制和兴奋的相对时间。索马和轴突终末之间的被动信号传输通过电紧张变换来检测，并量化为正弦电压波形的频率依赖性电压衰减。对于所探索的参数范围（轴突直径和长度，Ri），观察到的最低截止频率类似于300 Hz，这表明现实的暗视视觉信号将忠实地从索马传输到轴突末端，沿着轴突具有最小的被动衰减沿着。
Rod bipolar cells transmit visual signals from their dendrites, where they receive input from rod photoreceptors, to their axon terminals, where they synapse onto amacrine cells. Little is known, however, about the transmission and possible transformation of these signals. We have combined axon terminal recording in retinal slices, quantitative, light-microscopic morphological reconstruction and computer modelling to obtain detailed compartmental models of rat rod bipolar cells. Passive cable properties were estimated by directly fitting the current responses of the models evoked by voltage pulses to the physiologically recorded responses. At a holding potential of -60 mV, the average best-fit parameters were 1.1 mu F cm(-2) for specific membrane capacitance (C-m), 130 Omega cm for cytoplasmic resistivity (R-i), and 24 k Omega cm(2) for specific membrane resistance (R-m). The passive integration of excitatory and inhibitory synaptic inputs was examined by computer modelling with physiologically realistic synaptic conductance waveforms. For both transient and steady-state synaptic inhibition, the inhibitory effect was relatively insensitive to the location of the inhibition. For transient synaptic inhibition, the time window of effective inhibition depended critically on the relative timing of inhibition and excitation. The passive signal transmission between soma and axon terminal was examined by the electrotonic transform and quantified as the frequency-dependent voltage attenuation of sinusoidal voltage waveforms. For the range of parameters explored (axon diameter and length, R-i), the lowest cutoff frequency observed was similar to 300 Hz, suggesting that realistic scotopic visual signals will be faithfully transmitted from soma to axon terminal, with minimal passive attenuation along the axon.