Permeation of calcium ions through non-NMDA glutamate channels in retinal bipolar cells.
The conduction of calcium ions through glutamate-gated channels is important in the induction of long-term potentiation and may trigger other cellular changes. In retinal bipolar cells, which lack the N-methyl-D-aspartate (NMDA) type of glutamate-gated channel, calcium permeability through non-NMDA channels was examined. Changes in extracellular calcium concentration unexpectedly affected the reversal potential for glutamate-induced currents in a manner consistent with these channels being highly permeable to calcium. External magnesium ions promote desensitization of these non-NMDA channels in a voltage-independent way. Thus, in addition to non-NMDA channels that conduct only sodium and potassium, there is a class that is also permeable to calcium.
Gilbertson
T A
TA
Department of Zoology, University of California, Davis 95616.
Scobey
R
R
Wilson
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M
D000557:Ambystoma; D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D002463:Cell Membrane Permeability; D005971:Glutamates / Q000502:physiology; D066298:In Vitro Techniques; D007608:Kainic Acid / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D016202:N-Methylaspartate / Q000494:pharmacology; D017470:Receptors, Glutamate; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology; D017981:Receptors, Neurotransmitter / Q000187:drug effects / Q000502:physiology*; D012160:Retina / Q000166:cytology / Q000502:physiology*
D015220:Calcium Channels; D005971:Glutamates; D017470:Receptors, Glutamate; D016194:Receptors, N-Methyl-D-Aspartate; D017981:Receptors, Neurotransmitter; D016202:N-Methylaspartate; D007608:Kainic Acid; D002118:Calcium