Effect of nerve growth factor on neuronal apoptosis after spinal cord injury in rats

Toexplorethemolecularmechanismoftheprotectiveeffectofnervegrowthfactor(NGF)oninjuredspinalcord.Methods:TheposteriorT8(the8ththoracicsegment)spinalcordsof60Wistarratswereinjuredbyimpactscausedbyobjects(weighing10g)fallingfromaheightof2.5cmwithAllensway.Solutionwithnervegrowthfactors(NGF)wasgivento30rats(theNGFgroup)throughamicrotubuleinsertedintothesubarachnoidcavityimmediately,andat2,4,8,12and24hoursafterspinalcordinjury(SCI)respectively.Normalsaline(NS)withsamevolumewasgiventotheother30rats(theNSgroup)withthesamemethod.And5normalratsweretakenasthenormalcontrols.Theexpressionofbcl-2andbaxproteinsinspinalcordwasdetectedwithimmunohistochemistry.Theapoptoticneuronsinspinalcordweremeasuredwithterminaldeoxynucleotidyltransferase-mediateddUTP-biotinnickend-labelingofDNAfragments(TUNEL)staining.Results:Thepositiveexpressionofbcl-2proteinwasstronginthenormalcontrols,butdecreasedintheNSgroup,andincreasedsignificantlyintheNGFgroupascomparedwiththatoftheNSgroup(P<0.01).Thepositiveexpressionofbaxproteinwasalsostronginthenormalcontrols,butincreasedintheNSgroup,anddecreasedsignificantlyintheNGFgroupascomparedwiththatoftheNSgroup(P<0.01).ApoptoticneuronswerefoundintheNSgroup,andtheydecreasedsignificantlyintheNGFgroupascomparedwiththatoftheNSgroup(P<0.01).Conclusions:NGFcanprotecttheinjurednervetissuesthroughstimulatingtheexpressionofbcl-2protein,inhibitingtheexpressionofbaxproteinandinhibitingtheneuronalapoptosisafterSCI.