The study of antinociceptive effect of hydroalcoholic extract of Teucrium oliverianum (a plant used in southern Iranian traditional medicine) in rat by formalin test

Objective: Antinociceptive and anti-inflammatory activities of hydroalcoholic extract of Teucrium Oliverianum were investigated by formalin test model. This study was conducted in on the male Wistar rats, weighting 150-180 g. The animals were divided into seven groups (n = 7) and received 200, 400, 600 and 800 mg kg(-1) of hydroalcoholic extract of teucrium oliverianum intraperitoneally, respectively. Negative control group received normal saline (5 mL kg(-1)) and the positive control groups received 2.5 mg kg(-1) morphine and 300 mg kg(-1) aspirin, intraperitoneally respectively. The results showed that all doses of extract have significant analgesic effect (p < 0.05) in all studies times in comparison with negative control. The best result achieved with 600 mg kg(-1) of extract. The result revealed that the analgesic effect of the extract (600 mg kg(-1)) \was less than aspirin (300 mg kg(-1)) on the second phase of pain and less than morphine (2.5 mg kg(-1)) in both phases of the pain, more than aspirin in first phase of pain. One group of animals was treated with naloxone (1 mg kg(-1), i.p.) and suitable dose of extract (600 mg kg(-1), i.p.). Also, Naloxone inhibited analgesic effect of alcoholic extract of Teucrium Oliverianum. It can be concluded that the alcoholic extract of Teucrium oliverianum may exert its effect through opioid receptors, stimulating GABAergic system or promotes the release of endogenous opipeptides or decreasing free radicals.