Imaging of local and global sodium signals in astrocytes

Abstract

The use of fluorescent chemical indicator dyes enables the dynamic and quantitative imaging of intracellular sodium concentrations and activity-related sodium transients in astrocytes. Here we describe different approaches for the loading of cellular networks or single astrocytes with sodium-sensitive indicators in brain tissue. Fluorescence signals can then be detected and analyzed with conventional camera-based, wide-field imaging or by employing high-resolution multi-photon microscopy. We furthermore explain strategies for the induction of local and global sodium transients in astrocytes. Finally, we illustrate how fluorescence signals derived from such imaging experiments can be converted into absolute changes of sodium concentration in astrocytes based on an in situ calibration procedure.