THE KINETICS OF QUANTAL TRANSMITTER RELEASE FROM RETINAL AMACRINE CELLS
THE KINETICS OF QUANTAL TRANSMITTER RELEASE FROM RETINAL AMACRINE CELLS
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DOI：
10.1073/pnas.92.15.6896
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发表时间：
1995-07-18
影响因子：
11.1
通讯作者：
WILSON, M
中科院分区：
文献类型：
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作者：
BORGES, S;GLEASON, E;WILSON, M
在大多数突触中，递质的胞吐是由动作电位期间Ca 2+的进入触发的非常快速的过程。合理的预期是，胞吐的快速步骤之后是准备另一个囊泡用于胞吐的缓慢步骤，但这些步骤的身份和动力学目前尚不清楚。通过电压钳前和突触后神经元在一个孤立的对视网膜无长突细胞，我们已经测量了诱发突触电流和反应的单囊泡的发射器（minis）。从这些电流中，我们计算了持续的突触前去极化过程中胞吐的速率。我们在这里表明，对于这些细胞，释放与“开火和重装”的方案一致。大量的Ca 2+流入导致少量囊泡的快速释放，通常每个突触前神经元大约10个，可能对应于那些已经对接的囊泡。在胞吐峰值为每秒每个释放位点150个量子之后，持续的Ca 2+流入仅以每秒每个释放位点22个量子维持释放，这可能受到新鲜囊泡对接的速率限制。
Exocytosis of transmitter at most synapses is a very fast process triggered by the entry of Ca2+ during an action potential. A reasonable expectation is that the fast step of exocytosis is followed by slow steps readying another vesicle for exocytosis but the identity and kinetics of these steps are presently unclear. By voltage clamping both pre- and postsynaptic neurons in an isolated pair of retinal amacrine cells, we have measured evoked synaptic currents and responses to single vesicles of transmitter (minis). From these currents, we have computed the rate of exocytosis during a sustained presynaptic depolarization, We show here that for these cells, release is consistent with a scheme of ''fire and reload.'' Large Ca2+ influx causes the rapid release of a small number of vesicles, typically approximate to 10 per presynaptic neuron, likely corresponding to those vesicles already docked. After this spike of exocytosis whose peak is 150 quanta per release site per s, continued Ca2+ influx sustains release at only 22 quanta per release site per s, probably rate-limited by the docking of fresh vesicles.