Pathological states in the central nervous system lead to dramatic changes in the activity of neuroactive substances in the extracellular space, to changes in ionic homeostasis and often to cell swelling. To quantify changes in cell morphology over a certain period of time, we employed a new technique, three-dimensional confocal morphometry. In our experiments, performed on enhanced green fluorescent protein/glial fibrillary acidic protein astrocytes in brain slices in situ and thus preserving the extracellular microenvironment, confocal morphometry revealed that the application of hypotonic solution evoked two types of volume change. In one population of astrocytes, hypotonic stress evoked small cell volume changes followed by a regulatory volume decrease, while in the second population volume changes were significantly larger without subsequent volume regulation. Three-dimensional cell reconstruction revealed that even though the total astrocyte volume increased during hypotonic stress, the morphological changes in various cell compartments and processes were more complex than have been previously shown, including swelling, shrinking and structural rearrangement. Our data show that astrocytes in brain slices in situ during hypotonic stress display complex behaviour. One population of astrocytes is highly capable of cell volume regulation, while the second population is characterized by prominent cell swelling, accompanied by plastic changes in morphology. It is possible to speculate that these two astrocyte populations play different roles during physiological and pathological states.

• MeSH
• Astrocytes pathology   ultrastructure   MeSH
• Animals, Genetically Modified MeSH
• Glial Fibrillary Acidic Protein analysis   MeSH
• Microscopy, Confocal methods   MeSH
• Humans MeSH
• Models, Animal MeSH
• Brain pathology   ultrastructure   MeSH
• Mice MeSH
• Brain Diseases pathology   MeSH
• Green Fluorescent Proteins MeSH
• Imaging, Three-Dimensional * MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Review MeSH
• Names of Substances
• Glial Fibrillary Acidic Protein MeSH
• Green Fluorescent Proteins MeSH

[K(+)](e) increase accompanies many pathological states in the CNS and evokes changes in astrocyte morphology and glial fibrillary acidic protein expression, leading to astrogliosis. Changes in the electrophysiological properties and volume regulation of astrocytes during the early stages of astrocytic activation were studied using the patch-clamp technique in spinal cords from 10-day-old rats after incubation in 50 mM K(+). In complex astrocytes, incubation in high K(+) caused depolarization, an input resistance increase, a decrease in membrane capacitance, and an increase in the current densities (CDs) of voltage-dependent K(+) and Na(+) currents. In passive astrocytes, the reversal potential shifted to more positive values and CDs decreased. No changes were observed in astrocyte precursors. Under hypotonic stress, astrocytes in spinal cords pre-exposed to high K(+) revealed a decreased K(+) accumulation around the cell membrane after a depolarizing prepulse, suggesting altered volume regulation. 3D confocal morphometry and the direct visualization of astrocytes in enhanced green fluorescent protein/glial fibrillary acidic protein mice showed a smaller degree of cell swelling in spinal cords pre-exposed to high K(+) compared to controls. We conclude that exposure to high K(+), an early event leading to astrogliosis, caused not only morphological changes in astrocytes but also changes in their membrane properties and cell volume regulation.

• MeSH
• Astrocytes physiology   MeSH
• Potassium pharmacokinetics   MeSH
• Potassium Channels, Voltage-Gated physiology   MeSH
• Glial Fibrillary Acidic Protein metabolism   MeSH
• Gliosis physiopathology   MeSH
• Hypotonic Solutions pharmacology   MeSH
• Immunohistochemistry MeSH
• Hydrogen-Ion Concentration MeSH
• Rats MeSH
• Membrane Potentials drug effects   physiology   MeSH
• Patch-Clamp Techniques MeSH
• Spinal Cord cytology   MeSH
• Osmotic Pressure MeSH
• Rats, Wistar MeSH
• Sodium metabolism   MeSH
• Sodium Channels physiology   MeSH
• Cell Size MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Potassium MeSH
• Potassium Channels, Voltage-Gated MeSH
• Glial Fibrillary Acidic Protein MeSH
• Hypotonic Solutions MeSH
• Sodium MeSH
• Sodium Channels MeSH