Continuous vesicle cycling in the synaptic terminal of retinal bipolar cells
Continuous vesicle cycling in the synaptic terminal of retinal bipolar cells
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DOI：
10.1016/s0896-6273(00)80226-3
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发表时间：
1996-11-01
期刊：
影响因子：
16.2
通讯作者：
Job, C
中科院分区：
文献类型：
--
作者：
Lagnado, L;Gomis, A;Job, C
通过监测荧光染料FM 1 -43的摄取和丢失，研究了视网膜双极细胞突触末端的内吞和胞吐作用。在Ca 2+存在下的去极化刺激胞吐和胞吞的连续循环，其以高达每秒3800个囊泡的速率近似平衡。内吞作用1分钟内，囊泡可用于胞吐作用，约700，000个可释放囊泡特异性地定位于质膜2 μ m内的区域。使用NP-EGTA释放笼状Ca 2+，同时用Fura-2监测细胞质Ca 2+，表明亚微摩尔水平的Ca 2+刺激了连续的胞吐作用。有人认为双极细胞的带状突触只支持短暂的胞吐作用，但我们的结果表明，这种突触是专门用于连续分泌神经递质。
Endocytosis and exocytosis were investigated in the synaptic terminal of retinal bipolar cells by monitoring the uptake and loss of the fluorescent dye FM1-43. Depolarization in the presence of Ca2+ stimulated a continuous cycle of exocytosis and endocytosis that was approximately balanced at rates up to 3800 vesicles per s. Vesicles became available for exocytosis within 1 min of endocytosis, and about 700,000 releasable vesicles were specifically localized to a region within 2 mu m of the plasma membrane. Release of caged Ca2+ using NP-EGTA while simultaneously monitoring cytosolic Ca2+ with Fura-2 indicated that continuous exocytosis was stimulated by sub-micromolar levels of Ca2+. It has been suggested that the ribbon synapse of bipolar cells only supports transient exocytosis, but our results demonstrate that this synapse is specialized for the continuous secretion of neurotransmitter.