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Nanoscale diffusion in the synaptic cleft and beyond measured with time-resolved fluorescence anisotropy imaging.

ABSTRACT: 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 ~30% slower than in a free medium whereas inside neuronal dendrites this retardation is ~70%. In the synaptic cleft free nanodiffusion is decelerated by ~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.

SUBMITTER: Zheng K

PROVIDER: S-EPMC5299514 | biostudies-literature | 2017 Feb

REPOSITORIES: biostudies-literature

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Nanoscale diffusion in the synaptic cleft and beyond measured with time-resolved fluorescence anisotropy imaging.

Zheng Kaiyu K Jensen Thomas P TP Savtchenko Leonid P LP Levitt James A JA Suhling Klaus K Rusakov Dmitri A DA

Scientific reports 20170209

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 m ...[more]

PMID: 28181535

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Project description:Autofluorescence from the intracellular metabolite, NAD(P)H, is a biomarker that is widely used and known to reliably screen and report metabolic activity as well as metabolic fluctuations within cells. As a ubiquitous endogenous fluorophore, NAD(P)H has a unique rate of fluorescence decay that is altered when bound to coenzymes. In this work we measure the shift in the fluorescence decay, or average fluorescence lifetime (1-3 ns), of NAD(P)H and correlate this shift to changes in metabolism that cells undergo during apoptosis. Our measurements are made with a flow cytometer designed specifically for fluorescence lifetime acquisition within the ultraviolet to violet spectrum. Our methods involved culture, treatment, and preparation of cells for cytometry and microscopy measurements. The evaluation we performed included observations and quantification of the changes in endogenous emission owing to the induction of apoptosis as well as changes in the decay kinetics of the emission measured by flow cytometry. Shifts in NAD(P)H fluorescence lifetime were observed as early as 15 min post-treatment with an apoptosis inducing agent. Results also include a phasor analysis to evaluate free to bound ratios of NAD(P)H at different time points. We defined the free to bound ratios as the ratio of 'short-to-long' (S/L) fluorescence lifetime, where S/L was found to consistently decrease with an increase in apoptosis. With a quantitative framework such as phasor analysis, the short and long lifetime components of NAD(P)H can be used to map the cycling of free and bound NAD(P)H during the early-to-late stages of apoptosis. The combination of lifetime screening and phasor analyses provides the first step in high throughput metabolic profiling of single cells and can be leveraged for screening and sorting for a range of applications in biomedicine. © 2018 The Authors. Cytometry Part A published by Wiley Periodicals, Inc. on behalf of International Society for Advancement of Cytometry.

Dataset Information

Nanoscale diffusion in the synaptic cleft and beyond measured with time-resolved fluorescence anisotropy imaging.

Publications

Nanoscale diffusion in the synaptic cleft and beyond measured with time-resolved fluorescence anisotropy imaging.

Similar Datasets

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