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首页> 美国卫生研究院文献>The Journal of Neuroscience >Recovery from Short-Term Depression and Facilitation Is Ultrafast and Ca2+ Dependent at Auditory Hair Cell Synapses
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Recovery from Short-Term Depression and Facilitation Is Ultrafast and Ca2+ Dependent at Auditory Hair Cell Synapses

机译：从短期抑郁症和促进中的恢复是超快的并且依赖于听觉毛细胞突触中的Ca 2+。

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Short-term facilitation and depression coexist at many CNS synapses. Facilitation, however, has not been fully characterized at hair cell synapses. Using paired recordings and membrane capacitance measurements we find that paired-pulse plasticity at an adult frog auditory hair cell synapse depends on pulse duration and interpulse intervals. For short 20 ms depolarizing pulses, and interpulse intervals between 15 and 50 ms, facilitation occurred when hair cells were held at −90 mV. However, hair cells held at −60 mV displayed only paired-pulse depression. Facilitation was dependent on residual free Ca2+ levels because it was greatly reduced by the Ca2+ buffers EGTA and BAPTA. Furthermore, low external Ca2+ augmented facilitation, whereas depression was augmented by high external Ca2+, consistent with depletion of a small pool of fast releasing synaptic vesicles. Recovery from depression had a double-exponential time course with a fast component that may reflect the rapid replenishment of a depleted vesicle pool. We suggest that hair cells held at more depolarized in vivo-like resting membrane potentials have a tonic influx of Ca2+; they are thus in a dynamic state of continuous vesicle release, pool depletion and replenishment. Further Ca2+ influx during paired-pulse stimuli then leads to depression. However, at membrane potentials of −90 mV, ongoing release and pool depletion are minimized, so facilitation is revealed at time intervals when rapid vesicle pool replenishment occurs. Finally, we propose that vesicle pool replenishment kinetics is not rate limited by vesicle endocytosis, which is too slow to influence the rapid pool replenishment process.
机译：短期促进和抑郁同时存在于许多中枢神经系统突触中。然而，在毛细胞突触中尚未充分表征促进作用。使用成对的记录和膜电容测量，我们发现成年青蛙听觉毛细胞突触的成对脉冲可塑性取决于脉冲持续时间和脉冲间隔。对于短的20 ms去极化脉冲，以及15至50 ms之间的脉冲间隔，当毛细胞保持在-90 mV时会产生促进作用。但是，保持在-60 mV的毛细胞仅显示成对脉冲抑制。促进依赖于残余的游离Ca 2 + 的水平，因为Ca 2 + 缓冲液EGTA和BAPTA大大降低了该水平。此外，较低的外部Ca 2 + 促进了促进，而较高的外部Ca 2 + 增强了抑郁，这与一小部分快速释放的突触小泡的消耗是一致的。从抑郁中恢复具有双指数的时间过程，具有快速的成分，这可能反映了已耗尽的囊泡池的快速补充。我们认为，毛发细胞在体内具有更多的去极化静息样静息膜电位，其钙离子会渗入Ca 2 + 。因此，它们处于连续的囊泡释放，池消耗和补充的动态状态。在成对脉冲刺激过程中，进一步的Ca 2 + 大量涌入会导致抑郁。然而，在-90 mV的膜电位下，持续的释放和池耗竭被最小化，因此在发生快速的囊泡池补给的时间间隔显示出促进作用。最后，我们提出囊泡池补充动力学不受囊泡内吞作用的速率限制，该速率太慢以至于无法影响快速的池补充过程。

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