Lagnado L, Gomis A, Job C
MRC Laboratory of Molecular Biology, Cambridge, United Kingdom.
Neuron. 1996 Nov;17(5):957-67. doi: 10.1016/s0896-6273(00)80226-3.
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 microm 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.
通过监测荧光染料FM1-43的摄取和丢失，研究了视网膜双极细胞突触终末的内吞作用和外排作用。在Ca2+存在的情况下进行去极化刺激了一个连续的外排和内吞循环，在高达每秒3800个囊泡的速率下，二者大致平衡。囊泡在被内吞后1分钟内即可用于外排作用，并且约700,000个可释放囊泡特异性地定位于质膜内2微米的区域。使用NP-EGTA释放笼锁Ca2+，同时用Fura-2监测胞质Ca2+，结果表明亚微摩尔水平的Ca2+刺激了连续外排作用。有人提出双极细胞的带状突触仅支持瞬时外排作用，但我们的结果表明，这种突触专门用于神经递质的连续分泌。
