糖尿病大鼠甩尾潜伏期升高早期心脏感觉神经神经生长因子的表达变化

目的 观察糖尿病大鼠甩尾潜伏期(tail flick latency,TFL)升高早期上胸段背根神经节(dorsal root ganglion,DRG)、血清神经生长因子(nerve growth factor,NGF)含量变化. 方法 雄性SD大鼠18只,体重200～250 g,按随机数字表法分为对照组(C组,6只)和糖尿病组(DM组,12只).DM组大鼠经腹腔注射链脲佐菌素(streptozotocin,STZ)50 mg/kg.用疼痛甩尾仪每周测定大鼠TFL,监测躯体感觉神经病变的形成及变化.当DM组大鼠TFL显著升高时,取T1～T5节段DRG和血液样本,采用ELISA法测定标本中NGF水平. 结果 糖尿病造模5周末时,DM组大鼠TFL较C组显著升高.将TFL变化率＜100％的DM组大鼠设为DM1组(6只),TFL变化率≥100％的DM组大鼠设为DM2组(6只).NGF检测结果显示:与C组比较,DM1组DRG、血清中的NGF含量分别升高18％(P＜0.05)和16％(P＜0.05),DM2组DRG、血清中的NGF含量分别降低40％(P＜0.01)和14％(P＜0.05). 结论 糖尿病神经病变早期,随神经病变的加重,DRG、血清NGF含量表现为过表达和低表达,其机制和生物学意义值得进一步探讨.

Alteration of nerve growth factor in cardiac sensory nerves at early state of elevation of tail flick latency in diabetic rats

Objective The aim of this study is to investigate the change of nerve growth factor (NGF) expression level in upper thoracic segments dorsal root ganglion (DRG) which is participant in the transmission of heart nociception such as in the early time of elevation of tail flick latency (TFL) in diabetic rats.Methods Eighteen male SD rats,weighing 200-250 g,were randomly divided into control group(group C,n=6) and diabetic group(group DM,n=12).Rats in group DM were given streptozotocin(STZ,50 mg/kg,ip).Tail flick test apparatus was used to measure the TFL of rats every week to monitor the development of diabetic neuropathy.Serum and the DRG neurons in upper thoracic segments(T1-T5) innervating the heart were collected from diabetic animals when the diabetic animals presented significant elevation of TFL.Serum and DRG neurons of the age-matched non-diabetic control animals were also collected.The protein expression level of NGF in the DRG and serum were evaluated using enzyme-linked immunosorbent assay.Results The TFL significantly increased in diabetic rats in the 5th week after injection of STZ,compared with the values obtained from the age-matched non-diabetic rats in the control group(P＜0.05).Diabetic rats with lower increasing rates of TFL (less than 100％) were assigned to group DM1 (n=6) and the animals showing higher rates of elevation in TFL (greater than 100％) were defined as group DM2 (n=6).Interestingly,NGF expression level in the DRG and serum were increased by 18％(P＜0.05) and 16％(P＜0.05)respectively in group DM1,while the levels of NGF in group DM2 were decreased by 40％(P＜0.01) and 14％(P＜ 0.05) in the DRG and in serum respectively.Conclusions The finding of this study suggests that with deterioration of diabetic neuropathy in the early stage of diabetic neuropathy,the NGF in the DRG and in the serum were up-or down-regulated,of which the mechanism and biological significance were worth to be further investigated.