Bruns D, Jahn R
Howard Hughes Medical Institute, Yale University Medical School, New Haven, Connecticut 06510, USA.
Nature. 1995 Sep 7;377(6544):62-5. doi: 10.1038/377062a0.
Neurotransmitter release is mediated by Ca2+ dependent exocytosis of synaptic vesicles. Neither the amount of transmitter released from individual synaptic vesicles nor the kinetics of this process have yet been directly determined. Using carbon fibres as electrochemical detectors, we have measured release of the neurotransmitter serotonin from cultured neurons of the leech. This technique allowed us to monitor transmitter discharge from single synaptic vesicles as spike-like oxidation currents at high time resolution, providing new insight into the mechanism of neuronal exocytosis. Two types of signals were characterized, corresponding to exocytosis of small clear and large dense core vesicles present in these cells. A small vesicle discharges about 4,700 transmitter molecules with a time constant in the region of 260 microseconds, whereas large vesicles release their content of approximately 80,000 molecules with a time constant of about 1.3 ms. Release from both vesicle types is initiated rapidly, with a rise time of less than 60 microseconds, suggesting an abrupt opening of a preassembled fusion pore.
神经递质的释放是由突触小泡的Ca2+依赖性胞吐作用介导的。单个突触小泡释放的神经递质数量以及这一过程的动力学尚未直接确定。我们使用碳纤维作为电化学探测器，测量了来自水蛭培养神经元的神经递质5-羟色胺的释放。这项技术使我们能够以高时间分辨率将单个突触小泡的递质释放监测为尖峰状氧化电流，为神经元胞吐作用机制提供了新的见解。鉴定出了两种类型的信号，分别对应于这些细胞中存在的小清亮突触小泡和大致密核心突触小泡的胞吐作用。一个小突触小泡释放约4700个神经递质分子，时间常数在260微秒左右，而大突触小泡释放其约80000个分子的内容物，时间常数约为1.3毫秒。两种类型突触小泡的释放都迅速开始，上升时间小于60微秒，这表明预组装融合孔突然打开。
