Sulforhodamine 101 (SR101)
Red fluorescent dye. Preferential astrocyte marker. Also labels oligodendrocytes.
- Cell Imaging; IF
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It is a preferential astrocyte marker in vitro and in vivo, and is often used in neurophysiology experiments. It also marks oligodendrocytes.
The exact uptake mechanism of SR101 is unclear. It is believed that SR-101 is taken up by astrocytes and diffuses through astrocyte syncytia through gap junctions.
This dye is commonly used for in vivo brain imaging and allows in vivo oligodendrocyte imaging. It can be applied topically to the bare cortex or administered by injection.
The dye has a wide range of applications. For example, it is commonly used to identify astrocytes, counterstain astrocytes, and has been widely used as a calcium-sensitive dye to distinguish calcium signals derived from neurons and astrocytes.
Care and maintenance
Be careful when the dye used is less specific for astrocytes than originally reported, and since the dye labels oligodendrocytes, it cannot be assumed that all SR101 labeled cells are astrocytes.
The staining intensity of this dye also varies, depending on the brain area studied (it does not label astrocytes in brainstem slices as strongly or specifically as the hippocampus or cortex).
SR101 also has an effect on excitatory neuron activity and can induce cortical epilepsy-like activity.
Hülsmann et al. (2017) suggested that in order to minimize excitatory side effects, the SR101 concentration should be kept as low as possible, or a labeling procedure can be performed after the experiment.
If possible, researchers should take other measures in the experiment to confirm the specificity of SR101 staining (for example, electrophysiological whole-cell recording of SR101 labeled cells and post-mortem IHC).