Effects Of Intrathecal Injection Of Glial Cell-derived Neurotrophic Factor On Diabetic Neuropathic Pain In Rats And Its Possible Mechanism

Objective:By establishing a streptozocin-induced diabetic neuropathic pain（DNP）model,to investigate the effect of glial cell line-derived neurotrophic factor（GDNF）on the ethology of rats with diabetic neuropathic pain.To investigate the effect of GDNF on phosphorylated phosphatidylinositol 3-kinase（PI3K）,phosphorylated protein kinase B（AKT）,phosphorylated mammalian target of rapamycin（m TOR）and phosphorylated ribosomal protein S6 kinase（S6K）protein expression in the spinal dorsal horn in a rat model of diabetic neuropathic pain.And further investigate its mechanism of action.Methods:Male SD rats were randomly divided into control group（N group,n=10）and model group（n=40）.N group was injected with a single intraperitoneal injection of citric acid-sodium citrate buffer 2.8 m L/kg,and the model group was injected with a single intraperitoneal injection of 2%streptozotocin buffer 60 mg/kg.After 28 days of intraperitoneal injection,the rats were fasted for 12 h,and the blood glucose and mechanical threshold of tail pressing（TFT）of the tail vein of the rats were measured on an empty stomach.The DNP model was successful in rats with blood glucose>16.7 mmol/L and TFT decrease value>20%of the baseline value.A total of 29 DNP models were successfully completed this time,which were classified into the DNP model group（M group）.Twenty rats were randomly selected from M group and divided into DC group and DG group,with 10 rats in each group.Each rat in DG group was intrathecally injected with 2mg GDNF+10mL PBS;each rat in DC group was intrathecally injected with 10mL PBS;and each rat in N group was intrathecally injected with 10mL PBS.Intrathecal injections were given every other day for a total of 7 injections.The rats in each group were measured for the mechanical threshold of tail pressing（TFT）and paw withdrawal latency（PWL）before the modeling（on the day of modeling,when the intraperitoneal injection is not performed）,on the 3rd and 28st days after the modeling（after a single intraperitoneal injection）,and on the 1st,3rd,7th,and 14th days after the first intrathecal injection;After the last measurement,the rats were sacrificed,and the L_4-6spinal cord tissue was collected to measure the expression levels of phosphorylated PI3K,p-AKT,p-m TOR and p-S6K by Western blot.Results:On the 28st day after modeling,compared with the N group,the blood glucose of the rats in the M group was significantly increased（P<0.01）,and the TFT and PWL were also significantly decreased（P<0.01）;On the 14th day after the first intrathecal injection,compared with the DC group,the TFT and PWL of the rats in the DG group were significantly increased（P<0.01）,and the expressions of phosphorylated PI3K,p-AKT,p-m TOR and p-S6K in the L_4-6spinal cord tissue of the rats were significantly decreased（P<0.01）;On the 14th day after the first intrathecal injection,compared with the N group,the TFT and PWL of the rats in the DC group were significantly decreased（P<0.01）,and the expressions of phosphorylated PI3K,p-AKT,p-m TOR and p-S6K in the L_4-6spinal cord tissue of the rats were significantly increased（P<0.01）.Conclusion:1.GDNF can effectively relieve DNP symptoms in rats by intrathecal injection;2.GDNF can reduce the expression levels of phosphorylated PI3K,p-AKT,p-m TOR andp-S6K of the spinal dorsal horn of DNP rats by intrathecal injection;3.One of the analgesic mechanisms of GDNF:GDNF reduces the expression level of p-AKT by regulating the PI3K-AKT signaling pathway,thereby inhibiting the expression of p-m TOR and p-S6K,regulating the synthesis of cellular proteins,and finally exerting analgesic effect.