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Hypoxia increases calcium flux through cortical neuron glutamate receptors via protein kinase C
Author(s) -
Bickler P. E.,
Fahlman C. S.,
Ferriero D. M.
Publication year - 2004
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.2003.02203.x
Subject(s) - nmda receptor , glutamate receptor , hypoxia (environmental) , protein kinase c , calcium , chelerythrine , endocrinology , medicine , calcium in biology , biology , receptor , chemistry , phosphorylation , biochemistry , oxygen , organic chemistry
The effects of 30 s to 10 min hypoxia (PO 2 −10 mmHg) on glutamate receptor activity were studied in murine cortical neurons. Receptor activity was assessed as a rise in intracellular calcium concentration ([Ca 2+ ] i ) following a 10 s application of 1 m m glutamate or 100 µ m N ‐methy‐ d ‐aspartate (NMDA) in the presence of 0.1 m m Mg 2+ and 10 µ m glycine. Change in [Ca 2+ ] i elicited by glutamate increased 26% ( n = 192, p < 0.001) and that to NMDA by 74% ( n = 9, p < 0.01) during a 100‐s period of hypoxia. After 10 min hypoxia, responses to glutamate were 62% smaller than those in normoxia, with increased basal intracellular [Ca 2+ ] i predicting reduced receptor activity. When neurons were exposed to NMDA after 10 min of hypoxia, [Ca 2+ ] i increases were 12% smaller than after 100 s hypoxia, but still 53% larger than in oxygenated neurons ( n = 9, p = 0.01). Neurons expressed relatively similar amounts of NR2A, ‐B, ‐C, and ‐D subunits. The phosphorylation of NMDA NR1 subunits increased during hypoxia. Pre‐treatment of neurons with a protein kinase C (PKC) inhibitor (chelerythrine, 10 µ m ) prevented increases in N ‐methy‐ d ‐aspartate receptor (NMDAR) activity during hypoxia and reduced the phosphorylation of NR1 subunits. These results suggest that enhancement of glutamate receptor activity during the first minutes of hypoxia is mediated by phosphorylation of NMDARs by PKC and that other mechanisms, possibly involving intracellular calcium, limit glutamate receptor‐mediated calcium influx during longer periods of hypoxia.