Role Of Nerve Growth Factor In Painful Diabetic Rats

Partâ… The dynamic expression of NGF in dorsal horn and dorsal root ganglion of streptozotocin-induced diabetic ratsObjective To observe the dynamic expression of nerve growth factor (NGF) in dorsal horn and dorsal root ganglion (DRG) of streptozotocin-induced diabetic rats of neuropathic pain and to investigate the dependability of NGF protein level and mechanical threshold.Material and methods Fifty male Sprague-Dawley rats were randomly divided into 2 groups: 10 rats were selected as controls, another 40 rats was induced with a single intraperitoneal injection of streptozocin(55mg/kg) as diabetes. Mechanical threshold was assessed using Von Frey Hairs, before and 3 days and 1, 2, 4, 8 weeks after the formation of diabetes model. The expression of NGF in the dorsal horn and DRG was measured by western blot and immunohistochemistry at the same time points.Results Three days after administration of STZ, glucose level of more than 80% diabetic rats increased up to 16.7mmol/L and remained high after 8 weeks. The weight of diabetic rats became significantly lower than that of controls after 1 week and did not change significantly up to 8 weeks. The mechanical threshold was decreased 1 week after the formation of diabetes model and continued to 8 weeks. The NGF expression was reduced in 2 weeks and continued to 4 weeks in dorsal horn, and reduced in 1 week and continued to 8 weeks in DRG. The NGF protein level was positively correlated with mechanical threshold.Conclusion The expressionin of NGF in peripheral and central nervous system was decreased at the earlier period of streptozotocin-induced diabetic rats and it might contribute to the development and/or maintenance of painful diabetic neuropathy.Partâ…¡Changes of expression of NGF and mechanical threshold of painful diabetic rats treated with mNGFObjective To investigate the effect of exogenous mouse nerve growth factor (mNGF) on NGF expression and mechanical threshold in painful diabetic rats.Material and methods Forty male Sprague-Dawley rats were randomly divided into 2 groups: normal control group(Ctrl,n=10)and treatment group(n=30),and treatment group was divided into 3 groups: Saline-treatment group(Saline,n=10), low-dose mNGF-treatment group(mNGF1 , n=10) and high-dose mNGF-treatment group(mNGF2,n=10). The model of diabetes was established by the peritoneal injection of streptozocin (STZ). Mechanical threshold was assessed using Von Frey Hairs, before and 3 days and 1, 2, 4 weeks after the formation of diabetes model. The NGF expression in dorsal horn and dorsal root ganglion (DRG) was measured by western blot at 4 weeks.Results The mechanical threshold of mNGF1 and mNGF2 groups was elevated 2 weeks after treatment, compared with Saline group. The NGF expression of mNGF1 group was increased in DRG and the NGF expression of mNGF2 group was increased in DRG and dorsal horn.Conclusion Mechanical threshold was significantly increased after treatment of exogenous mNGF, which indicated the correlation between NGF and painful diabetic neuropathy.