Effects of intracellular calcium on GABAA receptors in mouse cortical neurons.
Using the patch-clamp technique, we studied the effect of intracellular Ca2+ on Cl- current gated by type A gamma-aminobutyric acid receptors (GABAA) in mouse cortical neurons. When the rapid Ca2+ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) was in the pipette solution, the GABA-activated Cl- current amplitude decreased over time to 49 +/- 7% of control. In contrast, equimolar replacement of BAPTA with ethylenebis(oxonitrilo)tetraacetate (EGTA) caused a 60 +/- 10% increase in GABA current. An increased intracellular Ca2+ concentration caused a transient augmentation of the GABA current. This effect of Ca2+ was concentration dependent (10 nM to 34 muM). Ca2+ increased the amplitude of the current by enhancing the maximal response to GABA rather than by changing the affinity of the receptor to GABA (EC50 = 5 +/- 0.4 muM vs. 7 +/- 0.3 muM). Both calmodulin (CaM) and a CaM kinase II inhibitor (200 muM) blocked the potentiating effect of Ca2+ suggesting that it was mediated by activation of CaM kinase II. We found that regulation of GABAA receptors by intracellular Ca2+ in cortical neurons has important physiological implications since the potentiating effect of increasing the intracellular Ca2+ on responses to GABA was mimicked by activating excitatory receptors with 100 muM N-methyl-D-aspartate (NMDA). These findings suggest that modulation of GABAA receptor activity by glutamate may be brought about via changes in intracellular Ca2+.
Aguayo
L G
LG
Laboratory of Neurophysiology, Department of Physiology, University of Concepcion, PO Box 152-C, Concepcion, Chile.
Espinoza
F
F
Kunos
G
G
Satin
L S
LS
D000818:Animals; D002118:Calcium / Q000494:pharmacology / Q000502:physiology*; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D002147:Calmodulin / Q000037:antagonists & inhibitors; D002478:Cells, Cultured; D002614:Chelating Agents / Q000494:pharmacology; D018118:Chloride Channels / Q000502:physiology*; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004553:Electric Conductivity; D004622:Embryo, Mammalian; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015640:Ion Channel Gating; D051379:Mice; D008810:Mice, Inbred C57BL; D016202:N-Methylaspartate / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D018079:Receptors, GABA / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism / Q000494:pharmacology
D002147:Calmodulin; D002614:Chelating Agents; D018118:Chloride Channels; D004791:Enzyme Inhibitors; D018079:Receptors, GABA; D004533:Egtazic Acid; D005680:gamma-Aminobutyric Acid; D016202:N-Methylaspartate; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium