The Effects Of Rap1 Protein On Anxiety-like Behavior In Mice And Its Possible Mechanisms

Anxiety is a mood state produced by the awareness of potential environment threats and challenges in the surrounding environment,it is closely related to the genetic background and the environment.Individuals who are in a state of anxiety often suffer from excessive fear and worry,and have a certain degree of cognitive,behavioral and physiological abnormalities.At present,with the rapid development of society,most of us have a high probability to encounter the challenges and the pressure frequently.Prolonged anxiety will seriously affect the individual's physical and mental health,and even lead to anxiety disorders and other mental disorders such as depression.Anxiety-like behavior test is a method to evaluate the individual's susceptibility to anxiety,as such plays an important role in the study of the formation mechanisms and development of anxiety.The small G protein Rap1,which is widely expressed in all kinds of cells,is one of the important molecular-switch proteins in the cell.Upon activation,it accepts signals from extracellular space and transfer these signals to the corresponding downstream proteins.A large body of evidence has proved that it plays an important role in cell proliferation,differentiation,survival,adhesion,migration and so on.Recent studies have found that the Rap1 is also involved in the regulation of synaptic structural and functional plasticity,which affects individuals' memory,cognition,emotional expression and other mental activities,and then affect their behavior.There has considerable evidence to suggest that the Rap1 in the forebrain is involved in learning and expression of fear in mice.However,it is unclear whether or not it is involved in the development and progression of anxiety disorders.In this study,we used forebrain-restricted rap1 knock-out mice(KO mice)and wild-type mice(WT mice)as experimental animals.By using the methods of behavioral test,western blotting and whole-cell patch clamp technique,we found that the level of anxiety-like behavior in KO mice was significantly lower than that in WT mice.In view of the ionic hippocampal glutamate receptors,including AMPA receptor and NMDA receptor,play an important role in the occurrence of anxiety disorder,we next detected the AMPA receptor and NMDA receptor trafficking in hippocampal tissue.The results showed that the contents of AMPA receptor and NMDA receptor on the plasma membrane of neurons in WT mice were less than those in KO mice,butthere was no significant difference in whole-cell extract.For the AMPA receptors have a strong association with miniature excitatory postsynaptic current(mEPSC),we recorded the mEPSC in hippocampal CA1 neurons.The results showed that the average amplitude of mEPSC of hippocampal CA1 neurons in KO mice was significantly higher than that in WT mice,and the cumulative distribution curve also shifted to right evidently.Logically,we then constructed a chronic restraint stress model in WT mice to explore the relationship between anxiety-like behavior and Rap1 protein deeply.The results shown that chronic restraint stress(CRS)can elevate the level of anxiety-like behavior in mice as well as activate Rap1 in hippocampus.In addition,the content of AMPA receptor and NMDA receptor on the plasma membrane of neurons in hippocampus of CRS-treated mice decreased,the same to the average amplitude of mEPSC and the AMPA receptor and NMDA receptor in whole-cell extract.Together,we concluded that: by affecting the glutamate receptor trafficking in hippocampal neurons,Rap1 can exerts an anxiogenic effect in anxiety-related behaviors in mice.In summary,our research provides a theoretical basis for the understanding of anxiety and the development of treatment strategies.