Abstract
BACKGROUND: Thymus species are well known medicinal plants which the previous studies suggested the involvement of the opioid system in them. OBJECTIVES: This study aimed to investigate the effects of methanolic extract and essential oil of aerial parts of Thymus daenensis (TD), an endemic aromatic medicinal plant of Iran, on morphine withdrawal syndrome in mice. MATERIALS AND METHODS: Experiments were performed in two groups of five, each group treated with extracts or essential oils of TD. Dependency was induced by subcutaneous injection of morphine for three consecutive days. On the fourth day, the last dose of morphine was injected two hours prior to intraperitoneal injection of naloxone while the extract or essential oil of TD was administered 30 minutes before naloxone. A period of 20 minutes after naloxone injection was considered the critical period of the withdrawal syndrome. The number of jumps, standing, leaning, and the weight of stools were recorded as withdrawal signs. RESULTS: The 200 mg/kg and 400 mg/kg doses of extract and all doses of essential oil decreased significantly the number of jumps, standing, leaning and the weight of stool. Administration of 100 mg/kg of extract only decreased the weight of stool and had no effect on the other factors. CONCLUSIONS: Extract and essential oil of TD attenuates morphine withdrawal behaviors in mice and may be useful in alleviating the signs and symptoms of opiate withdrawal syndrome in human.