Effect of elevated K+, hypotonic stress, and cortical spreading depression on astrocyte swelling in GFAP-deficient mice

• Published in: Glia 2001-09, Vol.35 (3), p.189-203
• Main Authors: Anděrová, Miroslava, Kubinová, Šárka, Mazel, Tomáš, Chvátal, Alexandr, Eliasson, Camilla, Pekny, Milos, Syková, Eva
• Format: Article
• Language: English
• Subjects: Animals; Astrocytes - drug effects; Astrocytes - metabolism; Astrocytes - pathology; Biological and medical sciences; Cell Membrane - drug effects; Cell Membrane - metabolism; Cell Membrane Permeability - drug effects; Cell Membrane Permeability - physiology; Cell Size - drug effects; Cell Size - physiology; cortex; Cortical Spreading Depression - drug effects; Cortical Spreading Depression - physiology; Diffusion - drug effects; diffusion parameters; extracellular potassium; Extracellular Space - drug effects; Extracellular Space - metabolism; Fluorescent Dyes - pharmacokinetics; Fundamental and applied biological sciences. Psychology; glial fibrillar acidic protein; Glial Fibrillary Acidic Protein - deficiency; Glial Fibrillary Acidic Protein - genetics; gray matter; intermediate filaments; Intermediate Filaments - drug effects; Intermediate Filaments - metabolism; Intermediate Filaments - pathology; Isolated neuron and nerve. Neuroglia; Isoquinolines - pharmacokinetics; Membrane Potentials - drug effects; Membrane Potentials - physiology; Mice; Mice, Knockout - anatomy & histology; Mice, Knockout - metabolism; Osmotic Pressure - drug effects; patch-clamp; Patch-Clamp Techniques; Potassium - metabolism; Potassium - pharmacology; Somatosensory Cortex - metabolism; Somatosensory Cortex - physiopathology; spinal cord; Spinal Cord - drug effects; Spinal Cord - metabolism; Spinal Cord - pathology; TMA+ iontophoretic method; Vertebrates: nervous system and sense organs
• ISSN: 0894-1491; 1098-1136
• DOI: 10.1002/glia.1084

Glial fibrillary acidic protein (GFAP) is the main component of intermediate filaments in astrocytes. To assess its function in astrocyte swelling, we compared astrocyte membrane properties and swelling in spinal cord slices of 8‐ to 10‐day‐old wild‐type control (GFAP+/+) and GFAP‐knockout (GFAP−/−) mice. Membrane currents and K+ accumulation around astrocytes after a depolarizing pulse were studied using the whole‐cell patch‐clamp technique. In vivo cell swelling was studied in the cortex during spreading depression (SD) in 3 to 6‐month‐old animals. Swelling‐induced changes of the extracellular space (ECS) diffusion parameters, i.e., volume fraction α and tortuosity λ, were studied by the real‐time iontophoretic tetramethylammonium (TMA+) method using TMA+‐selective microelectrodes. Morphological analysis using confocal microscopy and quantification of xy intensity profiles in a confocal plane revealed a lower density of processes in GFAP−/− astrocytes than in GFAP+/+ astrocytes. K+ accumulation evoked by membrane depolarization was lower in the vicinity of GFAP−/− astrocytes than GFAP+/+ astrocytes, suggesting the presence of a larger ECS around GFAP−/− astrocytes. Astrocyte swelling evoked by application of 50 mM K+ or by hypotonic solution (HS) produced a larger increase in [K+]e around GFAP+/+ astrocytes than around GFAP−/− astrocytes. No differences in α and λ in the spinal cord or cortex of GFAP+/+ and GFAP−/− mice were found; however, the application of either 50 mM K+ or HS in spinal cord, or SD in cortex, evoked a large decrease in α and an increase in λ in GFAP+/+ mice only. Slower swelling in GFAP−/− astrocytes indicates that GFAP and intermediate filaments play an important role in cell swelling during pathological states. GLIA 35:189–203, 2001. © 2001 Wiley‐Liss, Inc.