Intradendritic release of calcium induced by glutamate in cerebellar Purkinje cells.
The ability of excitatory amino acids to induce increases in the intracellular Ca2+ concentration ([Ca2+]i) of cerebellar Purkinje cells was examined by digital fluorescence ratio imaging of voltage-clamped Purkinje cells dialyzed with the Ca2+ indicator fura-2. Purkinje cells responded with large inward currents accompanied by increases in dendritic [Ca2+]i when challenged with the excitatory amino acid agonists glutamate and quisqualate. The rise in [Ca2+]i was transient and reached peak values of several hundred nanomolar. The response subsisted in the absence of extracellular Ca2+, a condition that eliminates Ca2+ entry through voltage-gated Ca2+ channels, indicating that Ca2+ arose in large part from an intracellular compartment. In support of this hypothesis, only the first agonist application elicited a [Ca2+]i increase in slices maintained in Ca(2+)-free medium, as expected if the intracellular stores become depleted. These results indicate that metabotropic glutamate receptors are functional in Purkinje cells and point to glutamate as a possible modulator of [Ca2+]i in these neurons.
Laboratoire de Neurobiologie, Ecole Normale Supérieure, Paris, France.
I
I
Llano
J
J
Dreessen
M
M
Kano
A
A
Konnerth
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D003712:Dendrites / Q000378:metabolism*; D004533:Egtazic Acid / Q000494:pharmacology; D004594:Electrophysiology; D016257:Fura-2; D005971:Glutamates / Q000494:pharmacology*; D018698:Glutamic Acid; D066298:In Vitro Techniques; D009994:Osmolar Concentration; D011689:Purkinje Cells / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D016318:Quisqualic Acid / Q000494:pharmacology; D013569:Synapses / Q000502:physiology
D005971:Glutamates; D018698:Glutamic Acid; D004533:Egtazic Acid; D016318:Quisqualic Acid; D002118:Calcium; D016257:Fura-2