Capacitance measurements in the mouse rod bipolar cell identify a pool of releasable synaptic vesicles.
Capacitance measurements in the mouse rod bipolar cell identify a pool of releasable synaptic vesicles.
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DOI：
10.1152/jn.00688.2006
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发表时间：
2006-11
影响因子：
2.5
通讯作者：
Zhen-Yu Zhou;Qunfang Wan;P. Thakur;R. Heidelberger
中科院分区：
文献类型：
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作者：
Zhen-Yu Zhou;Qunfang Wan;P. Thakur;R. Heidelberger
小鼠是理解神经元信号传导和突触通讯疾病的分子基础的重要模型系统。然而，最具特征的视网膜带状突触是那些非哺乳类脊椎动物。为了纠正这种情况，我们问是否可以使用时间分辨电容测量来跟踪分离的小鼠杆双极细胞中的突触囊泡动力学。结果表明，膜去极化触发了膜电容的增加，这是Ca（2+）依赖性的，并限于突触室，与胞吐作用一致。从一个完整的小鼠杆双极细胞的容易接近的索马记录的电容响应的幅度是相同的，直接从小突触终端记录，这表明，在这里提出的细胞的精心挑选的队列，轴突电阻不是一个显着的障碍电流。这一假设得到了被动膜特性分析以及具有和不具有突触末端的细胞中膜电容测量结果的比较的支持，并且由于正弦波频率（200- 1，600 Hz）对测量的电容增加没有影响而得到加强。随着Ca（2+）进入，电容响应的幅度增加，直到在空间平均端内钙约600 nM时达到平台。我们解释这个平台，名义上30 fF，作为对应的突触囊泡的可释放池。该测量的稳健性表明，电容测量可用于小鼠视杆双极细胞，以比较处理条件下的合并液大小。
The mouse is an important model system for understanding the molecular basis of neuronal signaling and diseases of synaptic communication. However, the best-characterized retinal ribbon-style synapses are those of nonmammalian vertebrates. To remedy this situation, we asked whether it would be feasible to track synaptic vesicle dynamics in the isolated mouse rod bipolar cell using time-resolved capacitance measurements. The results demonstrate that membrane depolarization triggered an increase in membrane capacitance that was Ca(2+) dependent and restricted to the synaptic compartment, consistent with exocytosis. The amplitude of the capacitance response recorded from the easily accessible soma of an intact mouse rod bipolar cell was identical to that recorded directly from the small synaptic terminal, suggesting that in the carefully selected cohort of cells presented here, axonal resistance was not a significant barrier to current flow. This supposition was supported by the analysis of passive membrane properties and a comparison of membrane capacitance measurements in cells with and without synaptic terminals and reinforced by the lack of an effect of sine-wave frequency (200-1,600 Hz) on the measured capacitance increase. The magnitude of the capacitance response increased with Ca(2+) entry until a plateau was reached at a spatially averaged intraterminal calcium of about 600 nM. We interpret this plateau, nominally 30 fF, as corresponding to a releasable pool of synaptic vesicles. The robustness of this measure suggests that capacitance measurements may be used in the mouse rod bipolar cell to compare pool size across treatment conditions.