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Dual Electrophysiological Recordings of Synaptically-evoked Astroglial and Neuronal Responses in Acute Hippocampal Slices
Published on: November 26, 2012
Sodium/calcium exchange in rat cortical astrocytes
W F Goldman1, P J Yarowsky, M Juhaszova
1Department of Physiology, University of Maryland School of Medicine, Baltimore 21201.
Summary
The sodium-calcium exchanger regulates cytosolic calcium in rat astrocytes. Reducing extracellular sodium or blocking calcium stores significantly increases intracellular calcium levels, indicating the exchanger
Area of Science:
- Neuroscience
- Cell Biology
- Biochemistry
Background:
- Cytosolic free Ca2+ concentration ([Ca2+]cyt) is critical for astrocyte function.
- The Na/Ca exchanger (NCX) is a key regulator of intracellular calcium homeostasis.
- Astrocytes play vital roles in neurotransmission and neuroprotection.
Purpose of the Study:
- To investigate the role of the Na/Ca exchanger in regulating [Ca2+]cyt in primary cultured rat cortical astrocytes.
- To elucidate the mechanisms by which Na/Ca exchange influences intracellular calcium dynamics.
- To determine the contribution of Na/Ca exchange to astrocyte responsiveness.
Main Methods:
- Digital imaging with fura-2 to measure [Ca2+]cyt.
- Manipulation of extracellular Na+ concentration ([Na+]o) and intracellular Na+ levels (using ouabain).
- Inhibition of intracellular Ca2+ sequestration using thapsigargin.
- Western and Northern blot analyses for Na/Ca exchanger protein and mRNA.
- Immunohistochemistry for exchanger localization.
Main Results:
- Reducing [Na+]o or increasing intracellular Na+ led to a significant rise in [Ca2+]cyt, particularly when intracellular Ca2+ sequestration was blocked.
- The low-[Na+]o-stimulated Ca2+ influx was dependent on extracellular Ca2+ but not via verapamil-sensitive channels or ryanodine-sensitive stores.
- Na/Ca exchanger protein and mRNA were detected in astrocytes, with the exchanger localized to the cell surface.
Conclusions:
- Na+ gradient reduction promotes net Ca2+ gain via Na/Ca exchange in astrocytes.
- Intracellular Ca2+ sequestration mechanisms normally buffer Na/Ca exchanger-mediated Ca2+ influx.
- The Na/Ca exchanger is crucial for regulating both cytosolic and intracellular store Ca2+ in astrocytes, influencing their response to stimuli.
