Dreosti Elena, Odermatt Benjamin, Dorostkar Mario M, Lagnado Leon
Medical Research Council Laboratory of Molecular Biology, Cambridge, UK.
Nat Methods. 2009 Dec;6(12):883-9. doi: 10.1038/nmeth.1399. Epub 2009 Nov 8.
To image synaptic activity within neural circuits, we tethered the genetically encoded calcium indicator (GECI) GCaMP2 to synaptic vesicles by fusion to synaptophysin. The resulting reporter, SyGCaMP2, detected the electrical activity of neurons with two advantages over existing cytoplasmic GECIs: it identified the locations of synapses and had a linear response over a wider range of spike frequencies. Simulations and experimental measurements indicated that linearity arises because SyGCaMP2 samples the brief calcium transient passing through the presynaptic compartment close to voltage-sensitive calcium channels rather than changes in bulk calcium concentration. In vivo imaging in zebrafish demonstrated that SyGCaMP2 can assess electrical activity in conventional synapses of spiking neurons in the optic tectum and graded voltage signals transmitted by ribbon synapses of retinal bipolar cells. Localizing a GECI to synaptic terminals provides a strategy for monitoring activity across large groups of neurons at the level of individual synapses.
为了对神经回路中的突触活动进行成像，我们通过与突触素融合，将基因编码钙指示剂（GECI）GCaMP2连接到突触小泡上。由此产生的报告分子SyGCaMP2检测神经元的电活动，与现有的细胞质GECI相比有两个优点：它能识别突触位置，并且在更宽的放电频率范围内具有线性响应。模拟和实验测量表明，线性响应的产生是因为SyGCaMP2对靠近电压敏感钙通道的突触前区短暂的钙瞬变进行采样，而不是对总体钙浓度的变化进行采样。斑马鱼体内成像表明，SyGCaMP2可以评估视顶盖中脉冲神经元的传统突触以及视网膜双极细胞的带状突触传递的分级电压信号中的电活动。将GECI定位到突触终末为在单个突触水平监测大量神经元的活动提供了一种策略。
