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Depolarization-induced alkalinization (DIA) in rat hippocampal astrocytes
1Department of Neurology, Yale University School of Medicine, New Haven, Connecticut 06510.
Journal of Neurophysiology
|December 1, 1994
Summary
Glial cells, specifically astrocytes, show increased intracellular pH (pHi) upon depolarization, a process known as depolarization-induced alkalinization (DIA). This alkalinization is largely dependent on bicarbonate and linked to changes in membrane potential.
Area of Science:
- Neuroscience
- Cellular Physiology
- Astrocyte Biology
Background:
- Glial cell depolarization is known to increase intracellular pH (pHi).
- Mammalian astrocytes exhibit depolarization-induced alkalinization (DIA).
- Understanding the mechanisms of DIA is crucial for comprehending astrocyte function.
Purpose of the Study:
- To characterize depolarization-induced alkalinization (DIA) in cultured rat hippocampal astrocytes.
- To investigate the role of bicarbonate in DIA.
- To determine the relationship between membrane potential changes and pHi shifts.
Main Methods:
- Cultured rat hippocampal astrocytes were loaded with the fluorescent pH indicator BCECF.
- Intracellular pH (pHi) was monitored using an imaging system.
- Experiments involved manipulating extracellular potassium ([K+]) and using HEPES or bicarbonate-buffered solutions; membrane potential was measured using whole-cell patch-clamp recording.
Main Results:
- Astrocyte pHi rapidly and reversibly increased (alkalinized) when extracellular potassium ([K+]) was elevated in bicarbonate-buffered solution, indicating bicarbonate-dependent DIA.
- DIA was significantly smaller in nominally bicarbonate-free HEPES-buffered solution.
- A direct relationship was observed between membrane potential shifts and pHi changes; depolarization, even without increased [K+], induced DIA, and barium application demonstrated this effect.
Conclusions:
- Depolarization-induced alkalinization (DIA) in astrocytes is a significant, bicarbonate-dependent process.
- Changes in membrane potential directly correlate with intracellular pH shifts in astrocytes.
- Astrocyte pHi regulation is closely linked to extracellular ion concentrations and membrane potential dynamics.
