Extracellular high K+ stimulates vesicular glutamate release from astrocytes by activating voltage-dependent calcium channels
✍ Scribed by Takahiro Yaguchi; Tomoyuki Nishizaki
- Publisher
- John Wiley and Sons
- Year
- 2010
- Tongue
- English
- Weight
- 394 KB
- Volume
- 225
- Category
- Article
- ISSN
- 0021-9541
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✦ Synopsis
Abstract
Extracellular high K^+^ (75 mM) increased intracellular Ca^2+^ concentrations in cultured rat hippocampal astrocytes, and the Ca^2+^ rise was abolished by deleting extracellular Ca^2+^ or cadmium, a non‐selective inhibitor of voltage‐dependent calcium channels (VDCCs). In the reverse transcription‐polymerase chain reaction analysis, cultured astrocytes expressed mRNAs for L type‐VDCC subunits such as α1B, α1C, α1D, and α1E. Extracellular high K^+^ (75 mM) stimulated glutamate release from astrocytes. The glutamate release was not prevented by the glutamate transporter inhibitor, L‐__tran__s‐pyrrolidine‐2,4‐dicarboxylic acid (PDC), or deleting extracellular Na^+^, but otherwise it was clearly inhibited by deleting extracellular Ca^2+^, cadmium, vesicular transport inhibitors such as brefeldin A, bafilomycin A1, and latrunculin B, or botulinum toxin‐A, an exocytosis inhibitor. Extracellular high K^+^ (75 mM) bleached fluorescent signals of FM1‐43, taken up into the vesicular membrane in astrocytes, that was also inhibited by deleting extracellular Ca^2+^, cadmium, brefeldin A, bafilomycin A1, latrunculin B, or botulinum toxin‐A, but not by PDC. Taken together, the results of the present study indicate that extracellular high K^+^‐evoked depolarization activates VDCCs expressed in astrocytes, causing an increase in intracellular Ca^2+^ concentrations through VDCCs, which triggers vesicular glutamate release from astrocytes, independently of reverse transport through glutamate transporters. J. Cell. Physiol. 225: 512–518, 2010. © 2010 Wiley‐Liss, Inc.