A study on the oxygen-glucose deprivation and glutamate tolerance of ground squirrels and the underlying mechanism

【摘要】：正Mammalian hibernators can survive hypoxia better than non-hibernators,but the mechanism is poorly known.A leading cause of stroke is ischemia,which is a shortage of oxygen and glucose.In this study,we compared the neuronal viability of Sprague Dawley rat and a mammalian hibernator-the ground squirrel(Spermophilus dauricus) in the oxygen-glucose deprivation(OGD) injury model.After 9-day culture in vitro,the cortical neurons were subjected to 3 h OGD treatment.The MTT result showed that about 13%of rat cortical neurons survived compared with 60%of ground squirrels.We next examined neuronal viability of ground squirrels and rats in glutamate injury model,as glutamate excitotoxicity plays a central role in ischemia injury.About only 30%rat cortical neurons survived 200μmol/L glutamate(24 h),while about 60%ground squirrel cortical neurons survived. LDH assay confirmed this result.To explore the mechanism underlying,we focused on two aspects:the glutamate receptor and signaling pathway.The specific inhibitor of NR2B-containing NMDA receptor ifenprodil could increase neuronal viability of rats,but not ground squirrels.Specific inhibitors of PKA,PKC and CaMKII were used to study the different response to glutamate injury of rats and ground squirrels.After blockade of PKA with H-89, rat neuronal viability was significantly increased;while blockade of PKC and CaMKII with chelerythrine chloride and KN-93 respectively,no significant change occurred.However,none of these inhibitors affected neuronal viability of ground squirrels in response to glutamate injury.These results suggested that cortical neurons of ground squirrels were more tolerant to OGD injury than rats,which was associated with the different responses to glutamate injury.NR2B-containing NMDA receptors and PKA signaling pathway were involved in this process.