Characterization of the social defeat stress model in mice and its consequences on the reinforcing effects of ethanol: involvement of corticosterone

• Grant number: 13/01342-2
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: June 01, 2013
• End date: December 31, 2013
• Field of knowledge: Biological Sciences - Pharmacology - Neuropsychopharmacology
• Principal Investigator: Isabel Marian Hartmann de Quadros
• Grantee: Gleice Midori Morita
• Host Institution: Escola Paulista de Medicina (EPM). Universidade Federal de São Paulo (UNIFESP). Campus São Paulo. São Paulo , SP, Brazil

Abstract

Chronic social defeat has been proposed as an animal model of social stress that produces a behavioral phenotype associated with depression, including signs of anhedonia, behavioral despair and impairments in social interaction. The present study will validate this model using Swiss albino mice, evaluating different depressive-like behaviors. Corticosterone, a stress hormone expected to be increased during depression, will also be measured. Finally, since some stressors promote an increased vulnerability to drug addiction, we will evaluate whether exposure to chronic social defeat stress increases preference for alcohol (ethanol).For this, we'll use Swiss male albino mice, which will be defeated daily during 10 days (stress group). After each defeat, the defeated animal will remain in the cage with the resident aggressor, separated by a perforated partition, allowing sensorial contact between animals. The next day, stressed mice will be defeated by a new aggressive resident, and so on, until completing the 10-day procedure. Another group of mice will serve as controls, and will spend 10 days living with another non-aggressive animal in the cage (with the partition). In Experiment 1, animals will be tested in the voluntary intake of a sucrose solution before, during and after the 10 days of social defeat, and will also be tested in the forced swim test (7-10 days after the last defeat). In Experiment 2, blood samples will be collected before, during and after the social defeat protocol for corticosterone assays, and animals will be tested in the elevated plus maze test and in the social interaction test (7 and 12 days after the last defeat, respectively). Finally, in Experiment 3, experimental animals will undergo the social defeat protocol, and after 7 days will be tested for ethanol-induced conditioned place preference. (AU)