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The Effect of Dexamethasone on Anxiety Related Behavior in Mice A.A. Vafaei PhD , H. Miladi-Gorgi MSc , A.A. Taherian MD2, A. Rashidy-Pour PhD Received: 08/05/06 Sent for Revision: 05/10/06 Received Revised Manuscript: 12/11/06 Accepted: 14/12/06 Background and Objective: Previous studies have suggested that activation of the glucocorticoid receptors may have a modulatory effect on fear and anxiety. Therefore, the aim of this study was to determine the role of glucocorticoid hormones on modulation of anxiety in elevated plus-maze model in mice. Materials and Methods: In this experimental study, 60 male mice (25-30 g) were included. They were randomely divided into test and control groups. The test group received different doses of dexamethasone, as an agonist of glucocorticoid receptors, at 0.1, 0.3, 1, 2 and 10 mg/kg, Subcutaneausly, and the control group received the same volume of 2% ethanol in normal saline 30 minutes before the evaluation of their behavior. Twenty five minutes after the injection, the mice were put in a black box for 5 minutes to induce their activity and stress. The animals were then individually transferred to a standard elevated pluse-maze in regulated time and the percentage of time spent in the open arms and the ratio of open arm entries to total entries in 5 mins was measured. Results: Results indicated that dexamethasone with the doses 0.3 and 1mg/kg, significantly reduced anxiety in mice (p<0.01). However, this effect was not observed at 0.1 and 2mg/kg. Our findings also showed that denamechasone at the dose of 10 mg/kg increased anxiety behavior in mice (p<0.01). Conclusion: The findings of this study indicated that glucocorticoids have important role in modulation of anxiety related behavior in a dose dependent manner using an elevated plus maze model in mice. Key words: Anxiety, Glucocorticoids, Dexamethasone, Mice