Study the Antinociceptive Effect of Intracerebroventricular Injection of Aqueous Extract of Origanum Vulgare Leaves in Rat: Possible Involvement of Opioid System

OBJECTIVE(S) The aim of study was to investigate the antinociceptive effect of intracerebroventricular (ICV) microinjection of Origanum vulgare (ORG) extract and possible involvement of opioid receptors. MATERIALS AND METHODS Cannula was inserted into left ventricle of male rats. Five days after surgery Tail Flick Latency (TFL) was measured after ICV microinjection of, ORG (1, 3 and 6 µg / rat). Effective dose of ORG was injected ICV in concomitant with morphine (2 mg/kg, IP), naloxone (2 mg / kg, IP) and saline (0.5 µl/rat) and TFL was recorded. RESULTS The co- administration of ORG extract with morphine showed a significant increase in TFL and naloxone, pretreatment significantly inhibited the antinociceptive activity of ORG and morphine. CONCLUSION The aqueous extract of ORG possesses antinociceptive activities in the tail-flick test in a dose dependent manner. ORG - induced antinociception may have been mediated by opioid systems.