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

Glia. 2001 Sep;35(3):189-203. doi: 10.1002/glia.1084.

Abstract

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 alpha and tortuosity lambda, 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 alpha and lambda 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 alpha and an increase in lambda 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Astrocytes / drug effects
  • Astrocytes / metabolism*
  • Astrocytes / pathology
  • Cell Membrane / drug effects
  • Cell Membrane / metabolism
  • Cell Membrane Permeability / drug effects
  • Cell Membrane Permeability / physiology
  • Cell Size / drug effects
  • Cell Size / physiology*
  • Cortical Spreading Depression / drug effects
  • Cortical Spreading Depression / physiology*
  • Diffusion / drug effects
  • Extracellular Space / drug effects
  • Extracellular Space / metabolism
  • Fluorescent Dyes / pharmacokinetics
  • Glial Fibrillary Acidic Protein / deficiency*
  • Glial Fibrillary Acidic Protein / genetics
  • Intermediate Filaments / drug effects
  • Intermediate Filaments / metabolism
  • Intermediate Filaments / pathology
  • Isoquinolines / pharmacokinetics
  • Membrane Potentials / drug effects
  • Membrane Potentials / physiology
  • Mice
  • Mice, Knockout / anatomy & histology
  • Mice, Knockout / metabolism
  • Osmotic Pressure / drug effects*
  • Patch-Clamp Techniques
  • Potassium / metabolism
  • Potassium / pharmacology*
  • Somatosensory Cortex / metabolism
  • Somatosensory Cortex / physiopathology
  • Spinal Cord / drug effects
  • Spinal Cord / metabolism
  • Spinal Cord / pathology

Substances

  • Fluorescent Dyes
  • Glial Fibrillary Acidic Protein
  • Isoquinolines
  • lucifer yellow
  • Potassium