The Regulatory Role Of OT In Sibling Companion Buffering Chronic Unpredictable Stress-induced Mood Disorders

Social environments have a great influence on animal emotions.Long-term exposure to social stress conditions leads to anxiety/depression-like behaviors.Social support can improve the health state,attenuate emotional and physical stress responses,reduce the level of anxiety and depression,and protect emotion and behavior.In recent years,much attention has been paid to the emotional withdrawn and mental illness due to the long-term lack of social support for teenagers,especially for only child.A large number of experiments show that companion as one of social support can effectively improve the emotional disorder.But the neural mechanism is still unclear.Studies have shown that oxytocin(OT)can affect animal recognition,reproduction,sexual behavior,parental behavior,partner preference,and other intimate social interactions.Mandarin voles(Microtus mandarinus)are socially monogamous rodents,and the establishment of the social relations involves the reward systems including dopamine and endogenous opioid neurotransmission.Oxytocin can significantly mediate this process.But there are few reports whether OT played key role in the process of research.Based on the above research,this paper studied the following questions.Firstly:whether the peers accompany could buffer anxiety and depression induced by Chronic Unpredictable Stress(Chronic Unpredictable Mild Stress,CUMS);Secondly:during the buffered process of peers accompany to anxiety and depression induced by CUMS in mandarin voles,we test the expression of OT in hypothalamus Paraventricular nucleus(PVN)and Supraoptic nucleus(SON);The last:whether exogenous OT regulated the buffered progress of peers accompany to anxiety and depression induced by CUMS in mandarin voles.Therefore,this study is divided into three parts.There are four groups in the first and second part:Single + CUMS,Single + Non-CUMS,Group + CUMS;Group +Non-CUMS.The first part of the experiment is building anxiety and depression model with CUMS,then test the behavior 15 days later,including open-field test(OFT),elevated plus-maze test(EPM)and forced swimming test(FST).The second part:Immunohistochemistry was used to test the expression of OT in PVN and SON,then using ELISA to test the serum levels of Glucocorticoid(CORT).There are four groups in the third part:Single + CUMS + OT,Single + CUMS + SAL(saline),Group +CUMS + OTA(Oxytocin receptor antagonist),Group + CUMS + SAL.All subjects exposure to CUMS,then inject OT/OTA or SAL in lateral ventricle 15 days later,finally use OFT,EPM and FST to test related behavior.The results showed that:1.In the OFT and EPM,the results found that CUMS induced anxiety behavior in males and females,and the peers accompany was able to buffer this effects.2.In the FST,the results revealed that CUMS can induce depression behavior in males.And peers accompany was able to buffer this effects.3.Immunohistochemical results indicated that OT expression decreased in anxious and/or depressive voles induced by CUMS,while peers accompany was able to buffer this effect.4.In ELISA,the experimental results showed the serum CORT were significantly increased in anxious and/or depressive males and females induced by CUMS,but the buffered effect of peers accompany is not obvious.5.Through the injection of exogenous OT/OTA and SAL,OFT and EPM showed that OT played essential role in buffered process of peers accompany to anxiety.6.Through the injection of exogenous OT/OTA and SAL in lateral ventricle,FST showed that OT played an important role in buffered process of peers accompany to depression in males.From the above results,peers accompany,as a kind of social support,has buffered effect on the anxiety and/or depression which induced by CUMS.Serum CORT was positive correlated with stress effects.OT system was essential in regulating this process.This study confirmed that the social support can protect the individual to reduce the negative effects of anxiety and depression.It provides a new thought that OT is pivotal in the process of regulating of social support on anxiety and depression.Further research is established to improve animal mood,and at the same time built a theoretical foundation on animal’s feeding and management.