The Role Of AMPA Receptor GluR1and GluR3Subunits Trafficking In Propofol Post-conditioning Induced Long-term Neuroprotection In A Rat Model Of Focal Cerebral Ischemia/Reperfusion

Objiective: Choosing the appropriate anesthetics for those patients who have suffered cerebral injury recently or with risk of perioperative stroke to preserve their compromised brain function is a major research endeavor for anesthetists. Propofol is one of the most popular agents used for clinical anesthesia. It has been suggested that propofol is an ideal anesthetic for neurosurgery because of its presumed beneficial effects on cerebral physiology (reduction in cerebral metabolic rate and cerebral blood flow, brain relaxation). Our previous research demonstrated that propofol at dose of20mg· kg-1· h-1infused at the onset of reperfusion for30min could provide neuroprotection to rats which had undergone2h of middle cerebral artery occlusion (MCAO) followed by22h of reperfusion. Howerer, it’s still unknown whether this neuroprotection could be sustained: long-term neuroprotective effect. In these days, some studies showed that AMPA receptor-mediated excitotoxicity is thought to play a critical role in central nervous systerm ischemic insults. Our previous study showed that AMPA receptor GluR2was involved in the neuroprotection of propofol. The aim of this study was to investigate the long-term effect of propofol post-conditioning against focal cerebral ischemia/reperfusion injury in rats and observe the change of AMPA receptor GluR1and GluR3subunit expression on the cell surface.Methods:Middle cerebral artery occlusion models were performed on healthy adults male Sprague-Dawley rats,250-280g. One hundred and seventy six rats were randomly divided into4groups with44rats in each group, including Sham group, I/R group, Pro group and Intra group. Cerebral ischemia was induced by60min of middle cerebral artery occlusion followed by long-term reperfusion. Rats were administered normal saline with equal volume to propofol, normal saline with equal volume to propofol, propofol20mg· kg-1· h-1,10%intralipid with equal volume to propofol at the onset of reperfusion for2h respectively. In the following28days, the neurological behavior scores (NBS) were assessed according to Garcia’s standard for evaluation. The percentage of cerebral infarct volume were detected by TTC staining on day1,7,14and28after ischemia. Two rounds of Morris water maze test were performed starting at day9and day23after ischemia respectively. The expression of total and surface AMPA receptor GluRl and GluR3subunit levels in hippocampus were measured by Western blot on day1,14and28after ischemia. The proliferation and differentiation of neural stem cells were detected by immunofluorescence. BrdU+NeuN double labelled cells of the hippocampus dentate gyrus were counted on day28after ischemia.Results: After a long-term observation, comparing with I/R group, propofol postconditioning at dose of20mg· kg-1· h-1improved the neurological behavioral scores and reduced the cerebral infarct volume(P<0.05), and increased the number of BrdU+NeuN labelled cells(P<0.05); In spatial learning and memory test, decreased escape latency was observed in Pro group(P<0.05), indicating propofol post-conditioning ameliorated the learning and memory ability of rats after ischemia; The expression of surface GluRl subunit was significantly lower in Pro group than in I/R group on day1、14after ischemia(P<0.05); The expression of surface GluR3subunit was significantly lower in Pro group than in I/R group1days after ischemia(P<0.05); The level of total GluRl and GluR3subunit level have no significantly difference among all groups(P>0.05); There was no significant difference between I/R group and Intra group in all index(P>0.05).Conclusion:Propofol post-conditioning at dose of20mg· kg-1· h-1but not lipid solvent provides a sustained neuroprotective effect, which can last for at least28days and inhibition of AMPA receptor GluRl and GluR3subunits trafficking may contribute to this long-term neuroprotection.