Glutamate-induced increases in intracellular Ca2+ in cultured frog tectal cells mediated by direct activation of NMDA receptor channels.
Influx of Ca2+ through NMDA channels may initiate the stabilization of coactive synapses during development of the retinotectal projection in frogs. Ca2+ imaging techniques were applied to cultured tectal cells to investigate whether excitatory amino acids cause a rise in [Ca2+]i. High [K+], NMDA, and glutamate increase [Ca2+]i in about 75% of the cells. NMDA and glutamate responses were completely blocked in the absence of extracellular Ca2+ and by the NMDA receptor or channel blockers APV and MK-801. The NMDA response was also blocked by Mg2+. Quisqualate and kainate produced little or no rise in [Ca2+]i. These studies indicate that when tectal cells are exposed to the retinal ganglion cell transmitter glutamate, the predominant means of Ca2+ entry is through NMDA channels.
Cline
H T
HT
Department of Molecular and Cellular Physiology, Stanford University School of Medicine, California 94305.
Tsien
R W
RW
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D016291:Dizocilpine Maleate / Q000494:pharmacology; D004594:Electrophysiology; D005971:Glutamates / Q000494:pharmacology*; D018698:Glutamic Acid; D007425:Intracellular Membranes / Q000378:metabolism; D007473:Ion Channels / Q000378:metabolism*; D007608:Kainic Acid / Q000494:pharmacology; D016202:N-Methylaspartate / Q000037:antagonists & inhibitors / Q000494:pharmacology; D016318:Quisqualic Acid / Q000494:pharmacology; D011894:Rana pipiens; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism*; D013477:Superior Colliculi / Q000166:cytology / Q000378:metabolism* / Q000502:physiology
D005971:Glutamates; D007473:Ion Channels; D016194:Receptors, N-Methyl-D-Aspartate; D018698:Glutamic Acid; D016202:N-Methylaspartate; D016291:Dizocilpine Maleate; D015763:2-Amino-5-phosphonovalerate; D016318:Quisqualic Acid; D007608:Kainic Acid; D002118:Calcium