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Membrane currents in CA1 pyramidal cells during spreading depression (SD) and SD-like hypoxic depolarization
G Czéh1, P G Aitken, G G Somjen
1Department of Physiology, Medical University of Pécs, Hungary.
Brain Research
|December 31, 1993
Summary
Spreading depression (SD) in rat neurons involves a large inward current and decreased membrane resistance. Hypoxic and normoxic SD showed similar electrical properties, suggesting a shared underlying mechanism.
Area of Science:
- Neuroscience
- Cellular Electrophysiology
Background:
- Spreading depression (SD) is a wave of intense neuronal activity followed by suppression.
- Understanding the ionic mechanisms of SD is crucial for neurological research.
Purpose of the Study:
- To investigate neuronal membrane current and resistance during spreading depression (SD) and SD-like depolarization.
- To differentiate between normoxic and hypoxic SD using electrophysiological methods.
Main Methods:
- Whole-cell patch clamp technique on rat hippocampal slices.
- Induction of SD using high K+ or electrical stimulation.
- Induction of SD-like depolarization via hypoxia.
- Precise membrane potential control using a reference extracellular electrode.
Main Results:
- A significant inward current (approx. 1.75 nA) and decreased input resistance (to 43% of control) were observed during SD.
- The apparent reversal potential for the SD current averaged near zero.
- Voltage-gated currents were lost during SD, with a small outward rectifying current persisting.
- Hypoxic and normoxic SD exhibited indistinguishable electrophysiological characteristics.
Conclusions:
- SD involves substantial changes in ion driving potentials and conductances.
- The observed decrease in membrane resistance during SD is less pronounced than previously reported.
- Hypoxia induces SD-like depolarization with similar electrical properties to normoxic SD.