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Unformatted text preview: A mouse model of depression induced by repeated corticosterone injections Yunan Zhao a , Ru Ma b , Jia Shen a , Hui Su a , Dongming Xing a , and Lijun Du a , , a Laboratory of Pharmaceutical Sciences, Department of Biological Sciences and Biotechnology, Tsinghua University, Beijing 100084, China b Biochemical Analysis Center, Xinxiang Central Hospital, Xinxiang 453000, China Received 19 August 2007; revised 26 November 2007; accepted 6 December 2007. Available online 14 December 2007. Abstract A rat model of depression has been recently developed by exogenous corticosterone administration. In this study, we further determined whether corticosterone administration also increased depression-like behavior in mice and explored the brain biochemical consequences of exposure to this administration paradigm. Mice received repeated injections of vehicle and 20 mg/kg of corticosterone for 1, 3 and 5 weeks, and then were subjected to the forced-swim and tail suspension tests. The results showed that repeated corticosterone injections increased immobility behavior in the forced-swim and tail suspension tests in a time-dependent manner. Meanwhile, this injection paradigm produced a time-related effect on tyrosine hydroxylase (TH) levels in the hippocampus of mice. These results are consistent with correlations in stress- induced depression models, and suggest that the repeated corticosterone injection paradigm provides a useful and reliable mouse model within which to further study the role of stress and glucocorticoids in depressive illness, as well as screen for antidepressants or preventive drugs. Keywords: Corticosterone; Depression; Animal model; Tyrosine hydroxylase; Stress; (Mouse) Article Outline 1. Introduction 2. Methods and materials 2.1. Animals and corticosterone administration 2.2. Forced swimming test and tail suspension test 2.3. Reverse transcription-polymerase chain reaction (RT-PCR) 2.4. Western blot analysis 2.5. Statistical analysis 3. Results 3.1. Body weight 3.2. Forced swimming test and tail suspension test 3.3. TH mRNA expression 3.4. TH protein levels 4. Discussion Acknowledgements References 1. Introduction According to large studies, depression is a severe illness with a lifetime prevalence of between 10 and 20%. It is estimated, by the World Health Organization, that depression will be the most important cause of disability in the world by the year 2020 ( Murray and Lopez, 1997 ). In terms of unipolar depression, it appears to have both a genetic and environmental basis. Twin studies suggest that about 2530% of the variance is genetic and that environmental factors account for about 75% of the variance ( Henn et al., 2004 ). The most important environmental factor is stress ( [Charney and Manji, 2004] and [Paykel, 2003] )....
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