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Na(+)-current expression in rat hippocampal astrocytes in vitro: alterations during development
H Sontheimer1, B R Ransom, A H Cornell-Bell
1Department of Neurology, Yale University School of Medicine, New Haven, Connecticut 06510.
Journal of Neurophysiology
|January 1, 1991
Summary
Sodium (Na+) currents in cultured hippocampal astrocytes change significantly over time. Initially resembling neuronal currents, they develop distinct "glial-type" properties after six days in culture.
Area of Science:
- Neuroscience
- Cell Biology
- Biophysics
Background:
- Astrocytes, a type of glial cell, play crucial roles in brain function.
- Sodium currents are essential for neuronal excitability but their role in astrocytes is less understood.
- Understanding astrocyte sodium currents is key to comprehending neuro-glial interactions.
Purpose of the Study:
- To investigate the expression and properties of sodium (Na+) currents in cultured rat hippocampal astrocytes.
- To determine how these Na+ currents change during development in vitro.
- To differentiate between early (neuronal-like) and later (glial-type) Na+ current characteristics in astrocytes.
Main Methods:
- Whole-cell patch-clamp recording was used to study Na+ currents in cultured hippocampal astrocytes.
- Astrocytes were identified using Lucifer yellow (LY) and immunostaining for glial fibrillary acidic protein (GFAP) and vimentin.
- Changes in Na+ current kinetics, inactivation, and current density were analyzed over a 20-day culture period.
Main Results:
- The proportion of astrocytes expressing Na+ currents decreased from 75% at day 1 to 30% by day 10.
- Early cultures (days 1-5) showed fast Na+ current kinetics and inactivation midpoints near -60 mV, resembling neuronal currents.
- After 6 days, astrocytes exhibited slower kinetics, hyperpolarized inactivation midpoints (around -85 mV), and altered current densities, indicating distinct "glial-type" properties.
Conclusions:
- Cultured hippocampal astrocytes exhibit dynamic changes in Na+ current expression and properties over time.
- Initially, astrocytes display Na+ currents similar to hippocampal neurons.
- After prolonged culture (≥6 days), astrocytes develop unique "glial-type" Na+ currents, suggesting a developmental shift in their electrophysiological characteristics.