The role of Ca2+ in the generation of spontaneous astrocytic Ca2+ oscillations

Neuroscience. 2003;120(4):979-92. doi: 10.1016/s0306-4522(03)00379-8.

Abstract

Astrocytes in the rat thalamus display spontaneous [Ca(2+)](i) oscillations that are due to intracellular release, but are not dependent on neuronal activity. In this study we have investigated the mechanisms involved in these spontaneous [Ca(2+)](i) oscillations using slices loaded with Fluo-4 AM (5 microM) and confocal microscopy. Bafilomycin A1 incubation had no effect on the number of spontaneous [Ca(2+)](i) oscillations indicating that they were not dependent on vesicular neurotransmitter release. Oscillations were also unaffected by ryanodine. Phospholipase C (PLC) inhibition decreased the number of astrocytes responding to metabotropic glutamate receptor (mGluR) activation but did not reduce the number of spontaneously active astrocytes, indicating that [Ca(2+)](i) increases are not due to membrane-coupled PLC activation. Spontaneous [Ca(2+)](i) increases were abolished by an IP3 receptor antagonist, whilst the protein kinase C (PKC) inhibitor chelerythrine chloride prolonged their duration, indicating a role for PKC and inositol 1,4,5,-triphosphate receptor activation. BayK8644 increased the number of astrocytes exhibiting [Ca(2+)](i) oscillations, and prolonged the responses to mGluR activation, indicating a possible effect on store-operated Ca(2+) entry. Increasing [Ca(2+)](o) increased the number of spontaneously active astrocytes and the number of transients exhibited by each astrocyte. Inhibition of the endoplasmic reticulum Ca(2+) ATPase by cyclopiazonic acid also induced [Ca(2+)](i) transients in astrocytes indicating a role for cytoplasmic Ca(2+) in the induction of spontaneous oscillations. Incubation with 20 microM Fluo-4 reduced the number of astrocytes exhibiting spontaneous increases. This study indicates that Ca(2+) has a role in triggering Ca(2+) release from an inositol 1,4,5,-triphosphate sensitive store in astrocytes during the generation of spontaneous [Ca(2+)](i) oscillations.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / pharmacology
  • Aniline Compounds / metabolism
  • Animals
  • Animals, Newborn
  • Anti-Infective Agents, Local / pharmacology
  • Astrocytes / drug effects
  • Astrocytes / metabolism*
  • Boron Compounds / pharmacology
  • Caffeine / pharmacology
  • Calcium / metabolism*
  • Calcium Channel Agonists / pharmacology
  • Calcium Signaling*
  • Dioxolanes / pharmacology
  • Drug Interactions
  • Enzyme Inhibitors / pharmacology
  • In Vitro Techniques
  • Methoxyhydroxyphenylglycol / analogs & derivatives*
  • Methoxyhydroxyphenylglycol / pharmacology
  • Microscopy, Confocal / instrumentation
  • Microscopy, Confocal / methods
  • Patch-Clamp Techniques / methods
  • Purines / pharmacology
  • Rats
  • Ryanodine / pharmacology
  • Thalamus / cytology
  • Thalamus / drug effects
  • Thalamus / metabolism*
  • Thimerosal / pharmacology
  • Xanthenes / metabolism

Substances

  • Aniline Compounds
  • Anti-Infective Agents, Local
  • Boron Compounds
  • Calcium Channel Agonists
  • Dioxolanes
  • Enzyme Inhibitors
  • Fluo 4
  • Purines
  • Xanthenes
  • 4-(2-amino-6-chloro-9H-purin-9-yl)-1,3-dioxolane-2-methanol
  • Ryanodine
  • Thimerosal
  • Caffeine
  • Methoxyhydroxyphenylglycol
  • 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester
  • 2-aminoethoxydiphenyl borate
  • Calcium
  • 3,4-dihydroxyphenylglycol