Objective:To evaluate the role of phosphatidylinositol 3-kinase (PI3K)/serine threonine protein kinase (Akt)/mammalian rapamycin target protein (mTOR) signaling pathway in edaravone-induced reduction of postoperative cognitive dysfunction in aged rats.Methods:Sixty healthy male Sprague-Dawley rats, aged 20 months, weighing 600-700 g, were divided into 4 groups ( n=15 each) using a random number table method: control group (group C), operation group (group O), edaravone group (group E) and PI3K inhibitor LY294002 group (group LY). The rats received laparotomy under 3% sevoflurane anesthesia in O, E and LY groups. Edaravone 3 mg/kg was intraperitoneally injected at 30 min before operation in E and LY groups, and LY294002 0.3 mg/kg was simultaneously injected via the tail vein in group LY. Open field test was performed at 3 days after surgery to evaluate the spontaneous activity of rats, then Morris water maze test was performed to evaluate the cognitive function of rats. The rats were sacrificed after the end of behavioral experiment to isolate hippocampal tissues for determination of the expression of phosphorylated PI3K (p-PI3K), phosphorylated Akt (p-Akt), phosphorylated mTOR (p-mTOR), synaptophysin (SYP) and postsynaptic density protein 95 (PSD 95) (by Western blot ) and dendrite length in hippocampal CA1 area (using Golgi staining). The density of dendrites was calculated. Results:There were no statistically significant differences in exercise speed, distance, and time of staying at the center between the four groups ( P>0.05). Compared with group C, the escape latency was significantly prolonged, the number of crossing the original platform was reduced, the expression of p-PI3K, p-Akt, p-mTOR, SYP and PSD-95 was down-regulated, the dendritic length of neurons in hippocampal CA1 region was shortened, and the density of neurons in hippocampal CA1 region was decreased in group O ( P<0.05). Compared with group O, the escape latency was significantly shortened, the number of crossing the original platform was increased, the expression of p-PI3K, p-Akt, p-mTOR, SYP and PSD-95 was up-regulated, the dendritic length of neurons in hippocampal CA1 region was prolonged, and the density of neurons in hippocampal CA1 region was increased in group E ( P<0.05). Compared with group E, the escape latency was significantly prolonged, the number of crossing the original platform was reduced, the expression of p-PI3K, p-Akt, p-mTOR, SYP and PSD-95 was down-regulated, and the dendritic length of neurons in hippocampal CA1 region was shortened, and the density of neurons in hippocampal CA1 region was decreased in group LY ( P<0.05). Conclusions:The mechanism by which edaravone reduces postoperative cognitive dysfunction is related to activating PI3K/Akt/mTOR signaling pathway and improving synaptic plasticity in aged rats.

Objective:To evaluate the effect of edaravone on the extracellular signal-regulated kinase (ERK)-cAMP responsive element binding protein (CREB) signaling pathway in the hippocampus of aged rats with postoperative cognitive dysfunction (POCD).Methods:Sixty SPF healthy male Sprague-Dawley rats, aged 20 months, weighing 650-700 g, were divided into 4 groups ( n=15 each) using a random number table method: control group (group C), POCD group (group P), edaravone group (group E) and ERK inhibitor group (group I). The rats received laparotomy under 3% sevoflurane anesthesia to prepare POCD model in P, E and I groups. Edaravone 3 mg/kg was intraperitoneally injected at 30 min before operation in E and I groups, ERK inhibitor PD98059 0.3 mg/kg was injected via the tail vein in group I. The open field test was performed at 3 days after operation to evaluate the spontaneous activity of rats, then Morris water maze test was performed to evaluate the cognitive function of rats on 3-7 days after operation. The rats were sacrificed after the end of Morris water maze test, and hippocampal tissues were obtained for determination of the expression of phosphorylated ERK (p-ERK), phosphorylated CREB (p-CREB), synaptophysin and postsynaptic density protein 95 (PSD-95) (by Western blot) and dendrite length and density of dendrites in hippocampal CA1 area (using Golgi staining). Results:Compared with group C, the escape latency was significantly prolonged after operation, the number of crossing the original platform was reduced, the expression of p-ERK, p-CREB, synaptophysin and PSD-95 was down-regulated, and the dendritic length and density of hippocampal neurons were reduced in group P ( P<0.05). Compared with group P, the escape latency was significantly shortened, the number of crossing the original platform was increased, the expression of p-ERK, p-CREB, synaptophysin and PSD-95 was up-regulated, and the dendritic length and density of hippocampal neurons were increased in group E ( P<0.05). Compared with group E, the escape latency was significantly prolonged, the number of crossing the original platform was reduced, the expression of p-ERK, p-CREB, synaptophysin and PSD-95 was down-regulated, the dendritic length of hippocampal neurons was shortened, and the density of hippocampal neurons was decreased in group I( P<0.05). Conclusions:The mechanism by which edaravone improves POCD may be related to activating ERK/CREB signaling pathway and changing synaptic plasticity in hippocampal CA1 region in aged rats.