Nanoscale diffusion in the synaptic cleft and beyond measured with time-resolved fluorescence anisotropy imaging
Nanoscale diffusion in the synaptic cleft and beyond measured with time-resolved fluorescence anisotropy imaging
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DOI：
10.1038/srep42022
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发表时间：
2017-02-09
影响因子：
4.6
通讯作者：
Rusakov, Dmitri A.
中科院分区：
文献类型：
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作者：
Zheng, Kaiyu;Jensen, Thomas P.;Rusakov, Dmitri A.
神经活动依赖于神经细胞内外纳米空间内的分子扩散，如突触裂隙或树突棘。到目前为止，在这种小范围内原位测量扩散是不可能的，但这一知识对于理解分子事件和电流的动力学至关重要，这些事件和电流塑造了整个大脑的生理信号。在这里，我们提出了时间分辨荧光各向异性成像与双光子激发显微镜相结合，以绘制体外脑片中纳米尺度的扩散系数。我们发现，在大脑组织间隙中，小分子的移动速度平均比在自由介质中慢30%，而在神经元树突内，这种延迟类似于70%。在突触间隙中，自由纳米扩散的速度减慢了约46%。这些量为释放的神经递质的受体作用、脑组织间隙的电导以及突触微环境中分子相互作用或构象变化的限速提供了以前无法获得的基本约束。
Neural activity relies on molecular diffusion within nanoscopic spaces outside and inside nerve cells, such as synaptic clefts or dendritic spines. Measuring diffusion on this small scale in situ has not hitherto been possible, yet this knowledge is critical for understanding the dynamics of molecular events and electric currents that shape physiological signals throughout the brain. Here we advance time-resolved fluorescence anisotropy imaging combined with two-photon excitation microscopy to map nanoscale diffusivity in ex vivo brain slices. We find that in the brain interstitial gaps small molecules move on average similar to 30% slower than in a free medium whereas inside neuronal dendrites this retardation is similar to 70%. In the synaptic cleft free nanodiffusion is decelerated by similar to 46%. These quantities provide previously unattainable basic constrains for the receptor actions of released neurotransmitters, the electrical conductance of the brain interstitial space and the limiting rate of molecular interactions or conformational changes in the synaptic microenvironment.