GLUTAMATE AND NON-GLUTAMATE RECEPTOR-MEDIATED TOXICITY CAUSED BY OXYGEN AND GLUCOSE DEPRIVATION IN ORGANOTYPIC HIPPOCAMPAL CULTURES

In vitro ischemia models have utilized oxygen, or oxygen and glucose d eprivation to simulate ischemic neuronal injury. Combined oxygen and g lucose deprivation can induce neuronal damage which is in part mediate d through NMDA receptors. Severe oxygen deprivation alone however can cause neuronal injury which is not NMDA mediated. We tested the hypoth esis that NMDA, or non-NMDA receptor mediated mechanisms may predomina te, to induce neuronal injury following severe oxygen deprivation depe nding on the presence of glucose. We found that NMDA receptor blockade using dizocilpine (MK-801), DL-2-amino-5-phosphonovaleric acid (APV), or CGS 19755, was highly effective in reducing CA1 injury in organoty pic hippocampal cultures, caused by complete oxygen and glucose depriv ation. Complete oxygen deprivation alone however, caused CA1 neuronal injury which was not diminished using NMDA receptor blockade alone wit h MK-801 or APV, or in combination with AMPA/kainate receptor blockade using 6-cyano-7-dinitroquinoxalone-2,3-dione (CNQX). Neuronal protect ive strategies which act primarily through non-glutamate dependent mec hanisms, including hypothermia, low chloride and calcium, and the free radical scavenger, alpha-phenyl-tert-butyl nitrone (PBN), provided ne uronal protection against complete oxygen, as well as combined oxygen/ glucose deprivation. Raising the pH using Hepes buffer during complete oxygen deprivation did not result in neuronal protection by NMDA rece ptor blockade. Partial oxygen deprivation alone, partial oxygen depriv ation combined with glucose deprivation, glucose deprivation alone, an d also glutamate exposure, all produced neuronal damage that was reduc ed by NMDA receptor block ade. The presence of glucose during complete oxygen deprivation appears to prevent glutamate receptor blockade fro m reducing neuronal injury in organotypic hippocampal cultures.