The aim of the present study is to investigate the influence of neural histamine in learned helplessness, emotional memory and neurogenesis of mice. Therefore, animals should be subjected to the chronic variable stress (CVS) for 7 days. During that period, the treated animals Will receive systemic injections of imipramine (10 mg/kg) or L-histidine (200 and 500 mg/kg) by volume of 2 ml/kg. After the CVS sessions, tests will be performed in the shuttle box (foot shock of 0.4 mA, duration of 10 s). The procedure in the shuttle box will involve the application of 30 escapable shocks signaled by a light (20 s). The shocks will be prevented or avoided when the animal crossed into the opposite compartment one in which the shock was presented. The fear memory and helplessness will be evaluated in the shuttle box in mice subjected to trials 24 h before and 24 h after the CVS, the helplessness component will be analyzed in animals taken directly to CVS and, after 24h, tested in the box. The measures will be: latency to emission of response, type of response (avoidance, escape or failure) and total transitions. Finally, 14 experimental groups will be formed relating stress/no stress conditions, sessions in the shuttle-box and pharmacological treatment. After the behavioral tests, the expression of c-Fos in the brain of those animals will be analyzed, in addition to the immunohistochemistry to evaluate the effects of the CVS and treatment on neurogenesis. The statistics include the Levene's test to check homogeneity of variance and ANOVA, followed by post-hoc appropriated to experimental design.
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