title: Modulation of intercellular calcium signaling in astrocytes by extracellular calcium and magnesium.
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.
authors.affiliation: Loma Linda University School of Medicine, Loma Linda, California, USA.
authors.forename: Charles
authors.initials: C
authors.lastname: Stout
authors.forename: Andrew
authors.initials: A
authors.lastname: Charles
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000172:deficiency* / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D002490:Central Nervous System / Q000166:cytology / Q000378:metabolism*; D004396:Coloring Agents; D017630:Connexins / Q000378:metabolism; D045604:Extracellular Fluid / Q000187:drug effects / Q000378:metabolism; D017629:Gap Junctions / Q000187:drug effects / Q000378:metabolism; D007424:Intracellular Fluid / Q000187:drug effects / Q000378:metabolism; D008274:Magnesium / Q000378:metabolism* / Q000494:pharmacology; D008275:Magnesium Deficiency / Q000378:metabolism; D008564:Membrane Potentials / Q000502:physiology; D051379:Mice; D010812:Physical Stimulation; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology
chemical_list: D004396:Coloring Agents; D017630:Connexins; D000255:Adenosine Triphosphate; D008274:Magnesium; D002118:Calcium