Glutamate- and AMPA-mediated calcium influx through glutamate receptor channels in medial septal neurons.
The Ca(2+)-fraction of the ion current flowing through glutamate receptor channels activated either by glutamate or by AMPA was determined in forebrain neurons of the rat medial septum. By combining whole-cell patch-clamp and fura-2 fluorometric measurements we found that, at negative membrane potentials and at an extracellular free Ca(2+)-concentration of 1.6 mM, the Ca(2+)-fraction of the current activated by glutamate is 5.7%. A pharmacological analysis of responses produced by ionophoretically-released glutamate demonstrated a large contribution of NMDA-receptors but a small contribution of AMPA/kainate receptors to these responses. Interestingly, also AMPA-mediated currents were associated with significant changes in Ca(2+)-sensitive fluorescence. The fractional Ca2+ current of AMPA-induced responses was 1.2 +/- 0.4% (n = 5).
Schneggenburger
R
R
I. Physiologisches Institut, Universität des Saarlandes, Homburg, Germany.
Tempia
F
F
Konnerth
A
A
D000818:Animals; D001923:Brain Chemistry / Q000187:drug effects / Q000502:physiology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism*; D003712:Dendrites / Q000187:drug effects / Q000378:metabolism; D005971:Glutamates / Q000494:pharmacology*; D018698:Glutamic Acid; D066298:In Vitro Techniques; D007478:Iontophoresis; D007608:Kainic Acid / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D016548:Prosencephalon / Q000166:cytology; D051381:Rats; D017208:Rats, Wistar; D017470:Receptors, Glutamate / Q000187:drug effects / Q000378:metabolism*; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000494:pharmacology*
D015220:Calcium Channels; D005971:Glutamates; D017470:Receptors, Glutamate; D016194:Receptors, N-Methyl-D-Aspartate; D018698:Glutamic Acid; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; D007608:Kainic Acid; D002118:Calcium