| Objective To prepare an animal model of delayed encephalopathy(DEACMP)caused by acute carbon monoxide poisoning,and the therapeutic effect of 10 Hz and 20 Hz repetitive transcranial magnetic stimulation(rTMS)on rats with delayed encephalopathy caused by acute carbon monoxide poisoning was studied,and the potential mechanism of improving DEACMP by rTMS was investigated.Methods Place qualified SD rats in a CO poisoning box and inhale CO gas with a concentration of 1000 ppm for 40 minutes and 3000 ppm for 20 minutes.Establish a DEACMP rat model after 21 days of poisoning.The normal rats served as the blank control group,and rats in the blank control group inhaled equal concentrations of air.Poisoned rats were randomized into CO poisoning group,10 Hz treatment group,and20 Hz treatment group.Rats in the treatment group were given 10 Hz and 20 Hz rTMS treatment,while the CO poisoning group rats were not treated with rTMS.Evaluate cognitive function of rats through Morris water maze experiment;Hematoxylin-eosin(HE)staining for differences in hippocampal histopathological manifestations;The levels of expression of brain-derived nerve growth factor(BDNF),tyrosine kinase receptor B(Trk B)and myelin basic protein(MBP)in rats were measured by enzyme-linked immunosorbent assay(ELISA);Immunohistochemical method was used to observe the expression of BDNF,Trk B and MBP in rat hippocampus,and the average optical density of these three factors was calculated by Image J software.The expression levels of BDNF,Trkb,and MBP were semi quantitatively measured,and the differences in the expression levels of BDNF,Trk B,and MBP in each group of rats were further compared.Combined with the changes in brain tissue structure and neural cell morphology of rats,the therapeutic effect of high-frequency rTMS at different frequencies on DEACMP rats was evaluated,and explored the underlying mechanisms.Results(1)Rats inhaling CO gas showed typical symptoms of CO poisoning:mild excitement and agitation in the early stage,with the increase of CO concentration and time,gradually appearing mental depression,weakness,shallow and rapid breathing,cherry red skin and mucous membrane around the mouth and extremities,coma or even death,autopsy of the dead rats revealed swelling and congestion of multiple organs,accompanied by local spotted hemorrhage.(2)The results of Morris water maze showed that the mean evasion latency of rats in the CO poisoning group,10 Hz treatment group and 20 Hz treatment group was significantly prolonged compared with the blank control group at 21 days of poisoning,and the discrepancy was statistically significant(P<0.05).After 14 days of rTMS treatment,the mean evasion latency of rats in the C0 poisoning group was significantly longer compared with the blank control group,and the difference was statistically meaningful(P<0.05),and the mean evasion latency of rats in the 10 Hz treatment group and20 Hz treatment group was significantly shorter compared with the poisoning group,respectively,and the difference was statistically meaningful(P<0.05).The differences were not statistically significant(P>0.05)when comparing the mean escape incubation period in the water maze of rats in the 10-Hz treatment group with that in the 20-Hz treatment group.(3)Hematoxylin-eosin(HE)staining:HE staining: Compared with the blank control group,the hippocampal histiocyte in the poisoned group were damaged to different degrees;Compared with the poisoning group,the 10 Hz treatment group had complete hippocampal cell structure and occasional neuronal damage.The 20 Hz treatment group had significantly improved the damage of hippocampal histiocyte,and no obvious necrotic focus was found.(4)The ELISA results showed that the expression levels of BDNF and Trk B were decreased and the expression levels of MBP were increased in the serum of the poisoned rats compared with the blank control group,and the differences were statistically significant(P<0.05).The expression levels of BDNF and Trk B in the serum of rats in the 10 Hz treatment group and 20 Hz treatment group were significantly higher than those in the moderate toxicity group,while the expression levels of MBP were lower than those in the poisoning group,with statistical significance(P<0.05).There was no statistically significant difference between serum BDNF,MBP and Trk B in the 10 Hz treatment group compared with the 20 Hz treatment group(P>0.05).(5)Immunohistochemical results showed that: compared with the blank control group,the tan expression in the poisoned group was slightly sparse,and the mean optical density values of BDNF and Trk B decreased;the tan expression in the10 Hz and 20 Hz treatment groups was relatively dense,and the mean optical density values of BDNF and Trk B were significantly higher than those in the poisoned group,and the differences were statistically significant(P<0.05);the positive expression of MBP in the poisoned group was relatively dense,and the mean optical density values of MBP were lower than those in the poisoned group,and the differences were statistically significant(P<0.05).The positive expression of MBP in the poisoned group was relatively dense,and the mean optical density value was significantly higher than that in the blank control group,while the positive expression in the 10-Hz and 20-Hz treatment groups was slightly sparse,and the mean optical density value of MBP was lower than that in the poisoned group,and the differences were statistically significant(P<0.05);there was no significant difference between the positive expression in the 10-Hz treatment group and the 20-Hz treatment group,and the mean optical density values of BDNF,MBP and Trk B were not statistically significant(P>0.05).Conclusion(1)High frequency(10Hz,20Hz)rTMS can effectively improve the cognitive function of rats with delayed encephalopathy caused by carbon monoxide poisoning;However,there was no significant difference in treatment efficacy between the 10 Hz treatment group and the 20 Hz treatment group.(2)High-frequency rTMS may improve the cognitive function of DEACMP rats by increasing BDNF,Trk B expressing level and decreasing MBP Expressing level,and it is speculated that it may be one of the molecular mechanisms by which rTMS improves the cognitive function of DEACMP rats.(3)rTMS is a safe and effective method for treating delayed encephalopathy caused by carbon monoxide poisoning in rats. |
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