Evaluation of anti-nociceptive effect of Thymus vulgaris essential oil in mice

Objective: Thymus vulgaris l (thyme) is an aromatic plant belonging to the lamiaceae family. It is a pleasant smelling perennial shrub, which grows in several regions in the world. Thymus vulgaris is a well-known aromatic plant and its essential oil and aromatic water are used in the different regions of Iran. Previous investigation has shown that Thymus vulgaris modulates pain. The aim of this work was to examine the role of Thymus vulgaris on acute and chronic pain in mice via intra-peritoneal administration by using Hot plate and Tail flick.Materials and Methods: In this study male albino mice (25-30 g.) in 4 groups (n=5) were used. 0.1, 03, 0.5 and 0.7mg/kg Thymus vulgaris essential oil were injected 30 minutes before pain assessment tests. Acute and chronic pain was assessed by Hot plate and Tail flick. Anti-nociception effect was defined as lack or delay in feet licking response to pin prick test and pressure from hemostat clamp compare to control. Time to the onset and duration of anti-nociception effect were recorded too. The results were analyzed using one-way analysis of variance and Duncan test as a post hoc. Results: Times (mean ± SD) to onset of and duration of loss of sensation, respectively in seconds were; 0.1 mg/kg Thymus vulgaris, 55 ± 7 and 572 ± 12, 0.3 mg/kg Thymus vulgaris 87 ± 3 and 878 ± 33; 0.5 mg/kg Thymus vulgaris 79 ± 4 and 756 ±18, 0.7 mg/kg Thymus vulgaris 72 ± 6 and 763 ± 52. Onset and duration times were significantly longer with 0.3 mg/kg Thymus vulgaris than the other three treatments (P 0.05).Conclusions: Results indicated that Thymus vulgaris have modulatory effects on acute and chronic pain. Further research is required to determine the mechanisms by which Thymus vulgaris essential oil exhibit the inhibitory effect on pain sensation.