Glutamate receptor agonists increase intracellular Ca2+ independently of voltage-gated Ca2+ channels in rat cerebellar granule cells.
Changes in membrane potential and cytosolic free Ca2+ concentrations, [Ca2+]i, in response to L-glutamate and glutamate receptor agonists were measured in rat cerebellar granule cells grown on coverslips. The membrane was depolarized by the application of L-glutamate and kainate, and by elevating the extracellular K+ concentration, as determined by using the membrane potential probe bisoxonol (DiBA-C4-(3)). The [Ca2+]i as measured with fura-2 was 220 nM on average under resting conditions and increased by raising the extracellular K+ and by applying L-glutamate, kainate, quisqualate or N-methyl-D-aspartate (NMDA). Verapamil and nifedipine reduced the high-K+ induced rise in [Ca2+]i but did not significantly affect the responses produced by NMDA, quisqualate and kainate, suggesting that the increase in intracellular Ca2+ in response to glutamate receptor agonists is primarily due to Ca2+ influx through receptor-coupled ion channels.
Holopainen
I
I
Department of Biomedical Sciences, University of Tampere, Finland.
Enkvist
M O
MO
Akerman
K E
KE
D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D002531:Cerebellum / Q000187:drug effects / Q000502:physiology*; D005971:Glutamates / Q000494:pharmacology*; D018698:Glutamic Acid; D066298:In Vitro Techniques; D007608:Kainic Acid / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D017470:Receptors, Glutamate; D017981:Receptors, Neurotransmitter / Q000187:drug effects / Q000502:physiology*; D014700:Verapamil / Q000494:pharmacology
D015220:Calcium Channels; D005971:Glutamates; D017470:Receptors, Glutamate; D017981:Receptors, Neurotransmitter; D018698:Glutamic Acid; D014700:Verapamil; D011188:Potassium; D007608:Kainic Acid; D002118:Calcium