| Background Heat stroke(HS)is a life-threatening condition,clinically diagnosed as a severe elevation in body temperature with central nervous system dysfunction.Cerebellum and cognitive function impairment is the most prominent neurologic sequelae,but there are no animal experimental study of long-term cognitive impairment coused by heat stroke.The mechanisms of cognitive impairment after heat stroke is not fully clear.Glutamate N-methyl-D-aspartate(NMDA)receptor can affect learning and memory ability by mediate synaptic plasticity and excitatory amino acids toxicity,participate physiological and pathological process in ischemic anoxia injury and nerve degeneration diseases.The expression of NMDA receptors in hippocampus after heat stroke remains unclear.Objective Establish HS rat models,observe the spatial learning and memory function 7days and21 days after heat stroke modeling respectively,test the expression of NR2A?NR2B in hippocampus organization in different periods,to explore the long-term cognitive impairment through heat stroke and the dynamic change of NMDA receptor expression in hippocampus and the possible relationship with cognitive impairment after heat stroke.Methods1.Heat stroke rats model establishment and grouping Establish HS rats model,HS rats were randomly divided into 3 groups: heat stroke0 day group(HS0,n=10),heat stroke 7days group(HS7,n=21),heat stroke 21 days group(HS21,n=21),surgery control group(Sham,n=18).HS0 rats were decapitated immediately after heat stroke occurred,preserved the hippocampus tissue.2.Morris Water Maze HS7 and HS21 groups were tested with Morris Water Maze 7 days and 21 days after modeling respectively,include place navigation test and space probe test.After the last time of the test,4 rats were randomly selected from each group,decapitated immediately and preserved the hippocampus tissue.3.Real-time PCR and Western Blot Analyze the change of NR2A?NR2B mRNA levels and the alterations of protein levels in hippocampus of rats from each group by applying Real-Time PCR and Western-blot detection technology.4.Statistical analysis Analyze data by Using SPSS20.0 and Graph Pad Prism 5 statistical software,inspection level: P<0.05.Results1.Place navigation tests The escaping latency of HS7 groups were longer than that in Sham group(P<0.05).1-3days,there were no significant difference between HS21 group and Sham group(P>0.05);4-5days,The escaping latency of HS21 groups were prolonged comparing with the Sham group(P<0.05).3-5days,HS21 group was shorter than that of HS7 group(P<0.05).2.Space probe tests The duration in the target quadrant: HS7 group was shorter than that of Sham group.HS21 group were increased compared with HS7 group(P<0.05).Frequency crossing the platform area: HS7 and HS21 groups were decreased compared with Sham group.There were no significant difference between HS21 group and HS7 group(P>0.05).3.RT-PCR(1)NR2A mRNA: HS0?HS7 and HS21 groups showed a trend of rise compared with the Sham group,rised to the peak in the 7th day and slightly declined in the 21 st day.Each HS group showed no statistical difference compared with Sham group(P>0.05).(2)NR2B mRNA: HS0?HS7 and HS21 groups showed a trend of rise compared with the Sham group,Each HS group showed no statistical difference compared with Sham group(P>0.05)4.Western-Blot(1)NR2A: HS0 were obviously decreased compared with the Sham group(P<0.05),there were no significant difference between HS7,HS21 group and Sham group(P>0.05).As the extension of time after the heat stroke,the expression of NR2 A showed a trend of gradual increase.(2)NR2B: HS0 were obviously decreased compared with the Sham group(P<0.05),there were no significant difference between HS7,HS21 group and Sham group(P>0.05).As the extension of time after the heat stroke,the expression of NR2 B showed a trend of gradual increase,rised to the peak in the 7th day and slightly declined in the 21 st day(P>0.05).Conclusion1.The spatial learning and memory ability in rats decreased after heat stroke,and heat stroke may remain long-term cognition deficits.2.The expreesion of NMDA receptors in hippocampal may have related to the cognitive impairment after heat stroke. |
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