Cell-type specific calcium responses in acute rat hippocampal slices

The identification of glial cells and neurons in brain slices is often difficult or uncertain. We have previously found that cultured rat cerebellar astrocytes and presumed astrocytes in acute brain slices, but not neurons, respond with cytosolic Ca (2+) transients following Ca2+ influx in low external K+ concentrations ( 1 mM; Cell Calcium 28 (2000) 247). We have now studied the possibility whether this Ca (2+) response can be employed to identify astrocytes during calcium imaging experiments. The Ca2+ responses to low and high (50 mM) K+ were investigated in cells in culture and in hippocampal slices. In the stratum radiatum of hippocampal slices, S-100B-positive cells, presumed to be astrocytes, preferentially accumulated Fluo-4, while pyramidal neurons, identified by neuron-specific enolase, showed much lower Fluo-4 fluorescence, fixed with ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDAC). 81% of the cells with prominent Fluo-4 fluorescence showed responses to low K+, and 86% of these cells were S-100B-positive. Our results suggest that the responsiveness to low K+ can help to identify astrocytes in acute brain slices. (C) 2002 Elsevier Science B.V. All rights reserved.