| Objective :The aim of the study was to analyze the relationship between the change of expression of CGRP and SP in myocardium,dorsal root ganglion(DRG)and serum,and desensitization of nociception,increased myocardial vulnerability observed in diabetic rats,and to investigate the correlation between desensitization of nociception and increased myocardial infarction after myocardial ischemia/reperfusion(I/R)injury.Methods :1.The establishment of the model of typeⅠ diabetic rat.60 male Sprague-Dawley rats(200-250g)were set as diabetes mellitus(DM)group given streptozotocin(STZ)50mg/kg(i.p.)to induce diabetes.The fasting blood glucose(FBG)> 16.7mmol/L lasting over a week were considered as diabetic rats.Another 30 male Sprague-Dawley rats(200-250 g)were set as controlled(C)group.Body weight,FBG and tail flick latency(TFL)in all rats were measured once a week.Enzyme-linked immunosorbent assay was used to measure the triglyceride in serum.2.The measurement of TFL and diabetic rats grouping: Diabetic rats were divided on the basis if the TFL in 5 weeks was longer than the double of TFL measured before the injection of STZ,into DM1 group(TFL in 5 weeks shorter than the double of initial TFL)and DM2 group(TFL in 5 weeks longer than the double of initial TFL)3.The difference of expression of CGRP and SP between two diabetic subgroup with different rates of hypoalgesia: We used histological immunofluorescence assay to performthe positioning study of CGRP and SP in the ischemia myocardium.Enzyme-linked immunosorbent assay(ELISA)was used to perform the quantitative determination of expression of CGRP and SP in myocardium,DRG(upper thoracic and lumbosacral)and serum.To analyze the results of measurements above,of two diabetic group.4.The difference of myocardial infarction between two diabetic subgroup with different rates of hypoalgesia after myocardial ischemia/reperfusion(I/R)injury.The evaluation of myocardial infarction area and myocardial ischemic was using Evans Blue and TTC staining.Terminal deoxynucleotide transferase-mediated dUTP nick end-labeling(TUNEL)assay was used to measure myocardial apoptosis.5.The measurement of nerve growth factor(NGF)and transient receptor potential vanilloid 1(TRPV1)in two diabetic subgroup: ELISA and Western Blot method were carried out to examine the changes of the expressions of NGF and TRPV1 in the ischemia myocardium.Results:1.After 5 weeks of diabetic duration,body weight of diabetic rats had decreased significantly compared with the normal controlled rats(P<0.05).Significant increases were observed in diabetic group in blood sugar and triglyceride in serum,compared with the normal controlled rats(P<0.01).2.Compared with control group,tail-flick latency was increased significantly after 5weeks of injection of STZ and the content of CGRP and SP in myocardium,dorsal root ganglion(DRG)and serum were significantly decreased in diabetic rats(P<0.05),and the content in DM2 group was lower than DM1 group significantly(P<0.05).3.Compared with control I/R group,the ratio of infarction area/ ischemic area,apoptosis rate and content of troponin were significantly higher in diabetic I/R group(P<0.05).In DM group,the three myocardial injury markers in DM2 group were all higher than DM1 group(P<0.05).Compared with corresponding sham group,the content of CGRP and SP increased significantly in control I/R group(P<0.05),and were non-significant in DM I/R group.4.Compared with the corresponding sham group,the expression of TRPV1 increased significantly in ischemic myocardium in controlled I/R group(P<0.05),and the change of TRPV1 in DM I/R group was non-significant.Compared with control group,we observed a significant reduction of TRPV1 in ischemic myocardium of diabetic rats(P<0.05)and there was no difference between DM1 and DM2 group.The expression of NGF in all groups: Compared with the corresponding sham group,the content of NGF increased significantly in ischemic myocardium of control I/R group and DRG(P<0.05),and there was no difference in DM I/R group.Compared with control group,the content of NGF increased in DM1 group significantly and decreased in DM2 group(P <0.05).Conclusion:1.After the administration of STZ,developed desensitization of nociception was observed in diabetic rats,showing a significantly prolonged TFL and we did not observe the change of TFL in normal rats.The rates of change of TFL in diabetic rats differed from each other,reflecting that development of sensory nerve deterioration in periphery and viscus was different,which correlated with the reduce of CGRP and SP in sensory nerve.2.DM2 group,with higher increasing rates of TFL were more susceptible to the myocardial ischemia/reperfusion(I/R)injury(P<0.05),which may correlated with decreased content of CGRP and SP,compared with DM1 group.3.The change of NGF and TRPV1 in diabetic rats may correlated with diabetic sensory neuropathy and the change in the content of CGRP and SP. |
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