| Objective: To observe the analgesic effect and related mechanism of peripheral acupoints electroacupuncture on superficial partial-thickness burn rats.Methods: This experiment consists of two parts:(1)Eighty SD rats were divided into sham injury group(SI),pure burn group(PB),electroacupuncture group(E),and sham electroacupuncture group(SE)according to the random number table,with 20 rats in each group.Right posterior leg of rats in group SI were sham injured,while superficial partial-thickness scald(hereinafter referred to as burn)model was reproduced on the right posterior leg of rats in the latter three groups.Electroacupuncture of peripheral acupoints of right posterior leg of rats(equivalent to Zusanli point and Sanyinjiao point of human)in group E were performed from post injury hour(PIH)12 on,while rats in group SE were treated with sham electroacupuncture,with 30 min each time,one time a day for 3 days.Before injury and at PIH 12,24,36,48,60,and 72,the threshold of mechanical pain of 5 rats in each group was tested,and the threshold of heat pain of another 5 rats in each group was tested.At PIH 48,brain tissue of 5 rats in each group was obtained to observe the morphology and distribution of astrocytes with positive expression of glia fibrillary acidic protein(GFAP)in periaqueductal gray(PAG)area by immunohistochemical staining,and the number of astrocytes was calculated.At the same time,brain tissue of the rest 5 rats in each group was obtained to determine the expression of GFAP of astrocytes in PAG area with Western blotting.Data were possessed with analysis of variance of repeated measurement,one-way analysis of variance,and SNK test.(2)The rats were divided into normal group,simple burn group,0.05 FC group,0.1FC group of drugs to fight drugs randomly,10 rats in each group.The position of PAG and the efficacy of FC were tested by using Nissl staining and immunofluorescence technique.Before and after burn 12 h,24h,36 h,48h phase points,the detection of experimental rats MWT,12 h test,in total 5 times.Then,5 rats in each group were collected,and the fresh brain tissue of PAG rats was collected.Results:(1)Compared with that in group SI,the threshold of mechanical pain of rats in groups PB and SE had no significant change before injury and at PIH 12(P>0.05),but was significantly decreased from PIH 24 to 72(P<0.05);while the threshold of mechanical pain of rats in group E was significantly decreased from PIH 36 to 72(P<0.05).The threshold of mechanical pain of rats in group E was significantly higher than that in groups PB and SE at PIH 24(P<0.05).Compared with that in group SI,the threshold of heat pain of rats in groups PB and SE had no significant change before injury(P>0.05),but was significantly decreased from PIH 12 to 72(P<0.05);while the threshold of heat pain of rats in group E was significantly decreased from PIH 12 to 60(P<0.05).The threshold of heat pain of rats in group E was significantly higher than that in groups PB and SE from PIH 24 to 48(P<0.05).The distribution of astrocytes with positive expression of GFAP in PAG area of rats in group SI was diffuse.The cell volume was small with cell body unobvious,and the projections were sparse,fine and short.The distribution of astrocytes with positive expression of GFAP in PAG area of rats in group PB was relatively concentrated.The cell body was hypertrophy and swelling,and the projections were increased and extended.The morphology and distribution of astrocytes with positive expression of GFAP in PAG area of rats in groups SE and E was similar to that in group PB.The numbers of astrocytes with positive expression of GFAP in PAG area of rats in groups SI,PB,E,and SE were 44±4,39±4,27±4,and 36±5,respectively.The number of astrocytes with positive expression of GFAP in PAG area of rats in group PB was significantly less than that in group SI(P<0.05),but similar to that in group SE(P>0.05).The number of astrocytes with positive expression of GFAP in PAG area of rats in group E was significantly less than that in groups PB and SE(P<0.05).The expressions of GFAP of astrocytes in PAG area of rats in groups SI,PB,E,and SE were 1.11±0.16,0.66±0.15,0.34±0.06,and 0.56±0.09,respectively.The expression of GFAP of astrocytes in PAG area of rats in group PB was significantly lower than that in group SI(P<0.05),but similar to that in group SE(P>0.05).The expression of GFAP of astrocytes in PAG area of rats in group E was significantly lower than that in groups PB and SE(P<0.05).(2)Under the microscope of low power microscope,the clear trajectory of the catheter was observed.In 48 h burned rats,PAG is not a drug side,showing a large number of activation of astrocytes,widely distributed and centralized;no drug side can be found a small amount of activated astrocytes,few and scattered distribution.Catheters burn treated rats,compared with sham injury group,burn group and drug group rats were significantly decreased heat pain threshold(P<0.01),in the injured rats after 12 ~ 48 h time period,there was no significant difference between simple burn group and 0.05 FC drug group thermally stimulated the pain threshold(P>0.05),0.1FC drug group the mechanical pain threshold increased significantly(P<0.01).Before and after the time point at 12 h after injury,0.1FC drug group was significantly higher than that of the mechanical pain threshold 0.05 FC Dayao group,the differences were statistically significant(P<0.001).Inflammatory factor sequence detection,visible 0.05 FC Dayao group and burn group CXCL7 was significantly higher than that of the other two groups.Conclusion: Electroacupuncture of peripheral acupoints can release the pain followed superficial partial-thickness burn in rats at early stage,and the possible mechanism is that it reduces the activation of astrocytes in PAG area. |
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