Modulation of intercellular calcium signaling in astrocytes by extracellular calcium and magnesium

✍ Scribed by Charles Stout; Andrew Charles

• Publisher: John Wiley and Sons
• Year: 2003
• Tongue: English
• Weight: 925 KB
• Volume: 43
• Category: Article
• ISSN: 0894-1491
• DOI: 10.1002/glia.10257

✦ Synopsis

Abstract

The extracellular concentrations of Ca^2+^ and Mg^2+^ are well known to play important roles in the function of the central nervous system. We examined the effects of extracellular Ca^2+^ and Mg^2+^ on ATP release and intercellular signaling in astrocytes. The extent of propagation of intercellular Ca^2+^ waves evoked by mechanical stimulation was increased by reduction of extracellular Ca^2+^ ([Ca^2+^]~o~) or Mg^2+^ concentration ([Mg^2+^]~o~) and was decreased by elevated [Mg^2+^]~o~. Reduction of extracellular Ca^2+^ concentration ([Ca^2+^]~o~) evokes intercellular Ca^2+^ signaling in astrocytes; a similar effect was observed in response to change from 5 mM [Mg^2+^]~o~ to 0 [Mg^2+^]~o~. Release of low‐molecular‐weight dyes and ATP was also activated by low [Ca^2+^]~o~ or [Mg^2+^]~o~ and inhibited by high [Ca^2+^]~o~ or [Mg^2+^]~o~. Astrocytes showed low [Ca^2+^]~o~–activated whole cell currents consistent with currents through connexin hemichannels. These currents were inhibited by extracellular Mg^2+^. We conclude that extracellular divalent cations modulate intercellular Ca^2+^ signaling in astrocytes by modulating the release of ATP, possibly via connexin hemichannels. © 2003 Wiley‐Liss, Inc.