Further evidence for calcium permeability of non-NMDA receptor channels in hippocampal neurons.
We have previously suggested that kainic acid (KA) increases the fluorescence of a fluoroprobe for Ca2+ via activation of the non-NMDA (N-methyl-D-aspartic acid) receptor in cultured hippocampal cells. The present study provides further evidence to support this suggestion. KA and NMDA increased the fluorescence occasionally in different subcellular loci of a single cell for each agonist, excluding the possibility that KA activated the NMDA receptor. KA elevated fluorescence in the cell whose membrane was voltage-clamped, thus eliminating possible Ca2+ entry through voltage-dependent channels. A monophasic response to KA was found to occur in the cells identified immunochemically as neurons. Even when the cells were cultured at different embryonic stages, KA responsiveness reached a peak at a rather fixed timepoint through the total age of neurons, while NMDA responsiveness continued to increase. This suggests that the Ca(2+)-permeable non-NMDA receptor is expressed according to a genetic schedule, but not to an artifactual effect of cell culture.
Ogura
A
A
Department of Neuroscience, Mitsubishi Kasei Institute of Life Sciences, Tokyo, Japan.
Nakazawa
M
M
Kudo
Y
Y
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism*; D002478:Cells, Cultured; D005865:Gestational Age; D006624:Hippocampus / Q000166:cytology* / Q000196:embryology; D015640:Ion Channel Gating / Q000187:drug effects; D016202:N-Methylaspartate / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D010539:Permeability; D051381:Rats; D018092:Kainic Acid Receptors; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism; D017981:Receptors, Neurotransmitter / Q000187:drug effects*; D013779:Tetrodotoxin / Q000494:pharmacology
D002118:Calcium; D015220:Calcium Channels; D016202:N-Methylaspartate; D018092:Kainic Acid Receptors; D016194:Receptors, N-Methyl-D-Aspartate; D017981:Receptors, Neurotransmitter; D013779:Tetrodotoxin