Effects Of 5-HT1A Receptors In Hippocampus And Sangpiaoxiao Powder On The Formation Of Background Fear Memory

Part one:Fear memory is a basic emotion response to potential danger when people or animals are subjected to threatening and catastrophic stimuli,which is critical for animals and human to survival.Appropriate fear can make the body adapt to the environment better,hypermnesia of fear memory can lead to psychopathologies,such as PTSD.The study found that the 5-HT system has an important regulatory effect on emotional memory,especially fear memory.Early research by our research group found that the activity of hippocampal Rac1 regulates the forgetting of contextual fear memory in rats.The 5-HT2 A receptor can regulate the activity of hippocampal Rac1 and there is an interaction between them.A large number of studies have shown that 5-HT1 A receptors are also involved in the regulation of fear memory,but the changes in hippocampal 5-HT1 A receptor expression and downstream molecules after fear learning are not clear at present.Whether 5-HT1 A receptors can also affect the activity of hippocampal Rac1 remains unknown.This topic discusses this issue.Objective: To investigate the changes of 5-HT1 A receptor expression in the hippocampus after learning the contextual fear and whether it can affect the rat’s contextual fear memory by regulating the activity of hippocampal Rac1.Methods:(1)The expression of 5-HT1 A receptor in hippocampus was detected by immunohistochemistry and Western blot after fear learning in rats.(2)Rats were divided into three groups,hippocampal CA1 were given vehicle+vehicle,vehicle+WAY100635(5-HT1 A receptor antagonist)and WAY100635 + NSC23766(Rac1inhibitor),and then the activity of hippocampal Rac1 was detected.(3)Coimmunoprecipitation to detect whether there is interaction between 5-HT1 A receptor and Rac1.(4)Hippocampal CA1 in rats was given vehicle+vehicle,Vehicle+WAY100635 or NSC23766+ WAY100635 pharmacological intervention to carry out contextual fear learning,and to test fear memory 24 h after learning.Results:(1)Immunohistochemistry and Western blot experiments after contextual fear learning showed that the expression of 5-HT1 A receptor in hippocampal was upregulated.(2)After hippocampal CA1 was administered to Vehicle+Vehicle,Vehicle+WAY100635 or NSC23766+WAY100635,WB experiment results showed that compared with the vehicle group,the activity of hippocampal Rac1 increased(p<0.05)in the Vehicle+WAY100635 group,and the activity of hippocampal Rac15-HT1 A decreased(p<0.001)in the NSC23766+WAY100635 group.(3)Immunoprecipitation to detect the existence of interaction between 5-HT1 A receptor and Rac1.(4)The three groups of rats had similar academic performance in contextual fear.The results of 24 h retrivel showed that compared with the vehicle group,the freezing time of Vehicle +WAY100635 group was reduced(p <0.01),and the freezing time of NSC23766 +WAY100635 group was similar to that of the control group.Conclusion:(1)The expression of 5-HT1 A receptor in hippocampal is upregulated after contextual fear learning in rats,with higher fear memory.(2)There is an interaction between 5-HT1 A receptor and Rac1.(3)After administration of 5-HT1 A receptor antagonist in CA1 area,the activity of hippocampal Rac1 is up-regulated,and Rac1 inhibitor can counteract the up-regulation of hippocampal Rac1 activity caused by 5-HT1 A receptor antagonist.(4)Inhibition of hippocampal 5-HT1 A receptor reduce contextual fear memory in rats,inhibition of hippocampal Rac1 activity can reverse the effect of 5-HT1 A receptor antagonist in rats.The above results suggest that 5-HT1 A receptor affects contextual fear memory by regulating the activity of hippocampus Rac1.Part two:Sangpiaoxiao Powder(spxs)is composed of Sang piao xiao,Yuan Zhi,keel,ginseng,fushen,angelica,tortoiseshell.It is a classic prescription for the treatment of phobia in china,but its mechanism of action is not clear.The hippocampus is a key brain area for learning and memory.Studies have found that stress can lead to changes in the structure and function of the hippocampus.Reversing the changes can help clear the fear memory of animals.We speculate that Sangshou San may affect the plasticity of hippocampus and play a role.To confirm this speculation,we conducted the following experiments.Objective:To explore the effect and potential mechanism of Sangqiaozhusan on the formation of conditional fear memory in rats.Methods: SD rats were randomly divided into two groups.They were respectively administered with Sangpiaoxiao Powder(spxs,0.425g/kg)or vehicle for one week,and then the rats were subjected to 3 times of 4m A footshock contextual fear learning for 1s,and the retrivel was performed 24 h after learning.Some rats were taken hippocampus for Western blotting and immunohistochemical staining before learning.Detection of expression changes molecules of learning and memory including p-CREB,c-fos,p-Pak1,Rac1-GTP.Results:(1)Administration of spxs,the expression of p-CREB in the CA1 area(p<0.001),CA3 area(p <0.001),and DG area(p <0.01)was increased,and the CA3 area c-fos expression was up-regulated(p <0.001);there was no difference in the expression of p-Pak1 and Rac1-GTP.(2)The behavioral results show that the freezing time after the third fear learning in the Sangqiaojiasan group is lower than that in the control group(p <0.05).There is no difference between the extraction of Sangqiaojiasan and the control group at 24 h.Conclusion: Sangpiaoxiao powder can induce the up-regulation of p-CREB and c-fos expression in hippocampus,and does not affect the expression of p-Pak1 and Rac1-GTP.Sangzhao San has a partial inhibitory effect on fear learning in rats.