Study On The Mechanism Of Hippocampal Endocannabinoid System Regulating Acute Stress-induced Emotional Response

Stress originates from various scenarios and environments changes in our daily lives,People face a variety of stresses,of which acute stress occurs every day and accompanies our growth.At present,the research on the neurological mechanism of acute stress mainly focuses on the mental trauma caused by high intensity or huge acute stress,such as the acute stress syndrome caused by huge mental trauma or the traumatic stress syndrome accompanied by huge geological disaster,but less attention has been paid to the multiple acute emotional reactions caused by mild or moderate stress.Futhermore,there is even less report on the neural mechanism of multiple acute emotional responses caused by different intensity of acute stress,so it is necessary to explore the neural mechanism behind different acute emotional responses.In this study,footshock,a common stress source of the acute stress,was used to establish animal models with different intensity of the footshock to induce different acute emotions,we observed the hippocampal brain region,which is highly correlated with acute stress emotional response,and observed the changes of endocannabinoid system,which plays an important regulatory function in the hippocampal brain region.Meanwhile,we explored the neural mechanism of different acute emotional responses induced by different intensity of acute stress,to further refine the various regulatory roles played by endogenous cannabis system in different acute emotional responses,and provide experimental evidence and theoretical support for better understanding the neural mechanism of different acute emotional responses.To accomplish these goals,the following experiments were carried out in this study.(1)C57/B6J wild-type mice were exposed to acute unpredictable 0.1 mA,0.3 mA,and 0.6 mA footshocks.Anxious behaviors of mice were evaluated by open-field and elevate plus maze behavior tests after footshocks exposure,and their effects on c-Fos protein and expression of endogenous cannabinoid receptor CB1 were observed by Western blot,and the changes of synaptic plasticity in hippocampal CA1 region were recorded by electrophysiological methods.(2)Mice were exposed to different intensity footshock by intraperitoneal and hippocampal pre-administration of CB1R receptor inhibitor AM281,to evaluate the effects of pre-treatment on anxiety behavior and expression of c-Fos and CB1 receptors in mice,and to record synaptic plasticity changes in hippocampal CA1 region by electrophysiological methods.(3)Glutamate and GABA-specific CB1R knockout tool mice were used to expose different intensity footshocks,to evaluate anxiety behavior and c-Fos expression in two groups of mice after footshocks exposure,and to record the changes of synaptic plasticity in hippocampal CA1 region.The results are as follows:(1)After the 0.1mA footshock test,mice showed alert behavior and LTP in hippocampal CA1 region was facilitated.After the 0.3mA footshock test,the mice showed moderate anxiety behavior and LTP damage in hippocampal CA1 area.At the end of the 0.6mA footshock test,the mice exhibited strong anxiety behavior,and the LTP damage in the hippocampus CA1 area increased.At the same time,the c-Fos protein expression in the hippocampus increased with the increase of foot shock and the CB1R protein expression in the hippocampus increased with the increase of electric shock intensity.(2)After pretreatment of mice with CB1R inhibitor AM281 in abdominal cavity and hippocampus,the 0.1 mA footshock induced alertness behavior switched to anxiety behavior,while the 0:3 mA and 0.6 mA footshock induced anxiety behavior increased,on the basis of which,the anxiety behavior of AM281 drug-pretreated mice was further aggravated.0.1 mA footshock induced LTP facilitation in hippocampal CA1 region,which was converted to LTP injury after AM281 drug pretreatment,and 0.3 mA and 0.6 mA footshock induced LTP injury in the original CA1 region.On the basis of LTP injury in the original CA1 region,AM281 pretreatment could not induce LTP.(3)Exposure of glutamate CB1R-specific knockout mice to different intensities of acute stress induced acute emotional responses similar to AM281-pretreated mice.The main behavioral manifestations were that alert behavior was converted into anxiety behavior and original anxiety behavior was enhanced,while LTP in hippocampal CA1 region was further aggravated on the basis of the original changes.(4)Exposure of GABA/CB1R-specific knockout mice to mild and moderate footshock induced anxiety behavior consistent with that of wild mice,but exposure to 0.6 mA footshock resulted in anti-anxiety behavior.The changes of LTP in hippocampus CA1 area of 0.1mA and 0.3mA footshock exposed GABA/CB1R knockout mice were consistent with those of wild mice.0.6mA footshock exposure did not cause LTP damage in hippocampus CA1 area,but resulted in LTP facilitation.In conclusion,different intensity of acute footshock can induce different acute emotional responses,and the main behaviors are acute alertness behavior and acute anxiety behavior.Meanwhile,different acute emotional responses may affect different changes of synaptic plasticity in hippocampal CA1 region.We demonstrated that the endocannabinoid system is involved in the regulation of acute emotional response by using AM281 pretreatment technology in the abdominal cavity and hippocampus,which regulates different acute emotional response transitions through the glutamate/GABA subsystem,while the hippocampus mainly regulates brain regions.We used different strains of CB1R specific knockout technology to confirm that hippocampal CB1R can accurately regulate acute alertness behavior and moderate anxiety behavior by inhibiting glutamate release,while hippocampal CB1R converts to inhibiting GABA release to achieve accurate regulation of stronger acute anxiety behavior.Finally,this study confirms that hippocampal CB1R can induce different acute emotional responses to different acute stresses by inhibiting the release of glutamate and GABA,which have opposite effects,respectively.This effect can promote the body to produce a matched acute emotional response according to different intensities of acute stress,and has important survival significance for the organism to produce an accurate behavioral response in the face of threats.