Study On The Buffer Effect And Neural Mechanisms Of Adolescents Associated With Chronic Unpredictable Mild Stress - Induced Emotional Disorder

The social environment has profound effects on physiology and behavior. Social environment has significant effects on anxiety/depression, and social support as one of the positive social environment was widely used to treat with emotional disorder, but its neuroendocrin mechanism was unknown. Animal model such as mice and rats don’t have complicated social behaviors, thus, it is difficcult to study the relationship between social support and anxiety/depression. Fortunately, monogamous voles have social behaviors which make them to be the animal model to study the social support.Mandarin vole is one of the monogamous animal with high sociality. Early social environment has effects on both its emotion and sociality. Because it is wild rodent, the life habit, social structure, behaviors are all differ from mice and rats. Mandarin voles adapt to physical and social environment so that the response to stress is different from mice and rats. Based on the above results and hypothesis, the present research use mice and mandarin voles to compare and modelling stress-induced emotion disorder by CUMS (chronic unpredictable mild stress), then study the buffering effects of sibling companion on CUMS-induced physical changes and emotional development and its neuromechanism.The current study found that:1) CUMS inhibit the gain of body weight in adolescent male mice. In group housing status, sibling companion as a social support buffered the CUMS-induced inhibition ofbody weight.2) Using open-field and elevated plus-maze to test the level of anxiety. The results showed that both model of housing and/or CUMS have no effects on the locomotor of adolescent male mice. CUMS induced anxiety in single housed mice. Sibling companion buffered CUMS-induced anxiety.3) Using forced swimming and sucrose preference to test the level of depression. The results showed that CUMS induced depression and sibling companion buffered CUMS-induced depression.4) The results of level of serum CORT showed that sibling companion increase the sensitivity to CUMS.5) Immunohistochemistry was used to test the expression of TH-immunoreactive (TH-IR) in VTA, GR-IR in CA1 of hippocampus and OT-IR in PVN and SON. The results showed that TH-IR in VTA was associated with social support, but it was not related to CUMS-induced emotional disorder. The expression of GR-IR in CA1andOT-IR in PVN and SON were participated in the process of sibling companion buffered CUMS-induced emotional disorder.6) We have compared ratio of body weight in different groups in adolescent mandarin voles. The results showed that sibling companion increase body weight of female voles when there was no CUMS. With CUMS, regardless of sibling companion, the body weight of female voles was inhibited. These suggested that either single housed or CUMS has ceiling effects on inhibition of body weight of females. But for males, just single housed combined with CUMS could suppress body weight.7) Using open-field and elevated plus-maze to test the level of anxiety. The results showed that CUMS induced anxiety both in females and males. Sibling companion buffered CUMS-induced anxiety.8) Using forced swimming and sucrose preference to test the level of depression. The results showed that CUMS induced depression on males and sibling companion buffered this CUMS-induced depression. And there was no effects on female adolescent mandarin voles.In conclusion, the results of the present research suggested there was species difference in response to CUMS. In mandarin voles, response to CUMSshows sex difference. Sibling companion as one kind of social support buffered CUMS-induced anxiety/depression which was modulated by oxytocin, dopamine and corticosterone system. Thus, the present study could make sure the rule of social support improving anxiety/depression, the neuroendocrine mechanism of social environment regulating anxiety/depression. The outcomes of this research also gave suggestion to study how to improve animal emotion and welfare, which in turn optimize animal raising and administration.