Calcium entry through kainate receptors and resulting potassium-channel blockade in Bergmann glial cells.
Glutamate receptors, the most abundant excitatory transmitter receptors in the brain, are not restricted to neurons; they have also been detected on glial cells. Bergmann glial cells in mouse cerebellar slices revealed a kainate-type glutamate receptor with a sigmoid current-to-voltage relation, as demonstrated with the patch-clamp technique. Calcium was imaged with fura-2, and a kainate-induced increase in intracellular calcium concentration was observed, which was blocked by the non-N-methyl-D-aspartate (NMDA) glutamate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and by low concentrations of external calcium, indicating that there was an influx of calcium through the kainate receptor itself. The entry of calcium led to a marked reduction in the resting (passive) potassium conductance of the cell. Purkinje cells, which have glutamatergic synapses, are closely associated with Bergmann glial cells and therefore may provide a functionally important stimulus.
Müller
T
T
Department of Neurobiology, University of Heidelberg, Germany.
Möller
T
T
Berger
T
T
Schnitzer
J
J
Kettenmann
H
H
D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D002531:Cerebellum / Q000502:physiology*; D004553:Electric Conductivity; D066298:In Vitro Techniques; D015640:Ion Channel Gating; D015759:Ionomycin / Q000494:pharmacology; D007608:Kainic Acid / Q000494:pharmacology; D051379:Mice; D009457:Neuroglia / Q000502:physiology*; D015221:Potassium Channels / Q000378:metabolism*; D018092:Kainic Acid Receptors; D017981:Receptors, Neurotransmitter / Q000378:metabolism*
D002118:Calcium; D015759:Ionomycin; D007608:Kainic Acid; D015221:Potassium Channels; D018092:Kainic Acid Receptors; D017981:Receptors, Neurotransmitter