Anxiolytic-like effects of essential oil from Thymus vulgaris was increased during stress

Tadaaki Satou, Mako Hayakawa, Yumi Goto, Yoshinori Masuo, Kazuo Koike

Index: 10.1002/ffj.3434

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Abstract

Abstract There is known to be a close relationship among anxiety, fatigue and stress. Here, we studied the anxiolytic-like effects of essential oil from Thymus vulgaris (EOT), while focusing on the relationship with stress. Male ICR mice inhaled (i.h.) EOT for 90 min. Mice were placed under three different conditions; isolated, intraperitoneal (i.p.) administration of saline or polyinosinic-polycytidylic acid (poly I:C). EOT did not show any significant anxiolytic-like effects in isolated mice. On the other hand, in brain fatigue model mice by poly I:C, EOT showed significant anxiolytic-like effects. EOT increased the absolute value in the elevated plus maze (EPM) tests in the brain fatigue model mice, while linalool and terpinen-4-ol in the brain with poly I:C were elevated when compared with isolated mice. Augmented concentrations of these components in the brain were also observed in mice with saline, i.p. These results suggest that the amount of volatile compounds transferred to the brain increased due to stress or inflammation. In the future, further investigation concerning the relationship between the blood brain barrier (BBB) and respiration is required. Concentrations of linalool in the brains of mice after inhalation (2 μL/L air EOT (A), 4 μL/L air EOT (B)). *p <0.05, ** p<0.01, Tukey-Kramer test, n = 4. Mice were kept under weak stress with isolation, moderate stress with saline i.p., and brain fatigue with poly I:C i.p.