Antinociceptive effect of the essential oil from Cymbopogon citratus in mice

The essential oil (EO) from leaves of Cymbopogon citratus increased the reaction time to thermal stimuli both after oral (25 mg/kg) and intraperitoneal (25-100 mg/kg) administration. EO (50-200 mg/kg, p.o. or i.p.) strongly inhibited the acetic acid-induced writhings in mice. In the formalin test, EO (50 and 200 mg/kg, i.p.) inhibited preferentially the second phase of the response, causing inhibitions of 100 and 48% at 200 mg/kg, i.p. and 100 mg/kg, p.o., respectively. On the other hand, the opioid antagonist naloxone blocked the central antinociceptive effect of EO, suggesting that EO acts both at peripheral and central levels. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.