Energy depletion during ischemia leads to disturbed ionic homeostasis and accumulation of neuroactive substances in the extracellular space, subsequently leading to volume changes in astrocytes. Confocal microscopy combined with 3D reconstruction was used to quantify ischemia-induced astrocyte volume changes in cortical slices of GFAP/EGFP transgenic mice. Twenty-minutes of oxygen-glucose deprivation (OGD) or oxygen-glucose deprivation combined with acidification (OGD(pH 6.8)) revealed the presence of two distinct astrocytic populations, the first showing a large volume increase (HR astrocytes) and the second displaying a small volume increase (LR astrocytes). In addition, changes in resting membrane potential (V(m)), measured by the patch-clamp technique, supported the existence of two astrocytic populations responding differently to ischemia. Although one group markedly depolarized during OGD or OGD(pH 6.8), only small changes in V(m) toward more negative values were observed in the second group. Conversely, acidification (ACF(pH 6.8)) led to a uniform volume decrease in all astrocytes, accompanied by only a small depolarization. Interestingly, two differently responding populations were not detected during acidification. Differences in the expression of inwardly rectifying potassium channels (Kir4.1), glial fibrillary acidic protein (GFAP), and taurine levels in cortical astrocytes were detected using immunohistochemical methods. We conclude that two distinct populations of astrocytes are present in the cortex of GFAP/EGFP mice, based on volume and V(m) changes during exposure to OGD or OGD(pH 6.8). Immunohistochemical analysis suggests that the diverse expression of Kir4.1 channels and GFAP as well as differences in the accumulation of taurine might contribute to the distinct ability of astrocytes to regulate their volume. 2008 Wiley-Liss, Inc.

• MeSH
• Astrocytes physiology   classification   pathology   MeSH
• Potassium Channels, Inwardly Rectifying metabolism   MeSH
• Electric Stimulation MeSH
• Financing, Organized MeSH
• Glial Fibrillary Acidic Protein genetics   MeSH
• Glucose deficiency   MeSH
• Hypoxia MeSH
• Ischemia pathology   MeSH
• Hydrogen-Ion Concentration MeSH
• Microscopy, Confocal MeSH
• Membrane Potentials physiology   MeSH
• Patch-Clamp Techniques MeSH
• Disease Models, Animal MeSH
• Cerebral Cortex pathology   MeSH
• Mice, Transgenic MeSH
• Mice MeSH
• Nerve Tissue Proteins metabolism   MeSH
• Taurine metabolism   MeSH
• Cell Size MeSH
• Green Fluorescent Proteins genetics   MeSH
• Animals MeSH
• Check Tag
• Mice MeSH
• Animals MeSH