Effects of chronic administration of Melissa officinalis L. extract on anxiety-like reactivity and on circadian and exploratory activities in mice

This study aimed to determine the effects of chronic (15 consecutive days of treatment) per os administration of Melissa officinalis L. extract (Cyracos®, Naturex) on anxiety-like reactivity in mice. As measured by HPLC, Cyracos® contains significant amounts of rosmarinic acid and the triterpenoids oleanolic acid and ursolic acid, which inhibit gamma-aminobutyric acid transaminase (GABA-T) activity and increase GABA levels in the brain (Awad et al., 2007; Awad et al., 2009).Thus, we evaluated Cyracos® use in independent groups of C57BL/6 mice with regard to anxiety-like reactivity in an elevated plus maze and an open field task. We found that Cyracos® significantly reduced anxiety-like reactivity in the elevated plus maze dose-dependently, but no significant effect was observed in the open field task. Parallel experiments in independent groups of mice showed that the Cyracos® dose at which it exerted anxiolytic-like effects in the elevated plus maze did not alter exploratory or circadian activities. Therefore, our results demonstrate that Cyracos® has anxiolytic-like effects under moderate stress conditions and does not alter activity levels.