Aim:This study was designed to investigate whether the activation of thephosphatidylinositol 3-kinase(PI3-K)/Akt pathway is required for thermal pre-conditioning to protect rat cerebellar granule neurons(CGN)against apoptosisinduced by low potassium,and to explore the possibility of a link between theupregulated heat shock protein(HSP)70 expression and Akt activation in theacquisition of neuroprotection induced by thermal preconditioning.Methods:CGN cultured for 8 d in vitro were switched to 5K medium for 24 h after thermalpreconditioning(TP;43.5 ℃ for 90 min,then 37 ℃ for 1 h).To study the role of thePI3-K/Akt pathway,a PI3-K inhibitor,LY294002(20 μmol/L)was added into thecultures 1 h before TP.3-(4,5-dimethylthiazol-2-yl)2,5-diphenyltetrazolium bro-mide(MTT)assay and fluorescein diacetate staining were used to determine cellviability.Hoechst 33258 staining and agar gel electrophoresis were used to testthe morphological and biological characters of CGN.Western blot analysis wasemployed to detect the levels of phospho-Akt,phospho-glycogen synthase ki-nase 3β(GSK3β) Akt,GSK3β,and HSP70.Results:TP protected CGN againstapoptosis induced by low potassium.LY294002 inhibited the neuroprotectiveeffect on CGN induced by TP.TP induced a robust activation of Akt and theinactivation of GSK3β via PI3-K.Furthermore,the activation of the PI3-K/Aktpathway by TP persisted for 24 h in the 5K cultures.LY294002(20 μmol/L)failedto inhibit the upregulated HSP70 expression induced by TP.Conclusion:Theactivation of the PI3-K/Akt pathway is required for TP to protect CGN againstapoptosis induced by low potassium,but the neuroprotective effect by Akt acti-vation is not mediated through the downstream induction of HSP70 expression. Aim: This study was designed to investigate whether the activation of the phosphatidylinositol 3-kinase (PI3-K) / Akt pathway is required for thermal pre-conditioning to protect rat cerebellar granule neurons (CGN) against apoptosis induced by low potassium, and to explore the possibility of a link between the regulated heat shock protein (HSP) 70 expression and Akt activation in the acquisition of neuroprotection induced by thermal preconditioning. Methods: CGN cultured for 8 d in vitro were switched to 5 K medium for 24 h after thermal preconditioning for 90 min then 37 ° C for 1 h). To study the role of the PI3-K / Akt pathway, a PI3-K inhibitor, LY294002 (20 μmol / L) was added into the cultures 1 h before TP.3- (4 , 5-dimethylthiazol-2-yl) 2,5-diphenyltetrazolium bro-mide (MTT) assay and fluorescein diacetate staining were used to determine cell viability. Hoechst 33258 staining and agar gel electrophoresis were used to test the morphological and biological characters of CGN. Western blot analysis wasem ployed to detect the levels of phospho-Akt, phospho-glycogen synthase ki-nase 3β (GSK3β) Akt, GSK3β, and HSP70. Results: TP protected CGN againstapoptosis induced by low potassium. LY294002 inhibited the neuroprotective effect on CGN induced by TP.TP induced a robust activation of Akt and the activation of GSK3β via PI3-K.Furthermore, the activation of the PI3-K / Aktpathway by TP persisted for 24 h in the 5K cultures. LY294002 (20 μmol / L) failed to inhibit the upregulated HSP70 expression induced by TP.Conclusion: Theactivation of the PI3-K / Akt pathway is required for TP to protect CGN againstapoptosis induced by low potassium, but the neuroprotective effect by Akt acti-vation is not mediated through the downstream induction of HSP70 expression.