Naloxone-resistant antinociceptive activity in the essential oil of Psidium pohlianum Berg.

The antinociceptive activity of the essential oil from leaves of Psidium pohlianum Berg (Myrtaceae) was evaluated in mice using three different nociceptive tests, namely, formalin, low temperature hot-plate (51 ± 1°C) and caudal compression method. Oral administration of Psidium oil (100, 200 and 400mg/kg) produced a dose-related significant antinociception in a hot-plate test, in a manner similar to morphine but appeared more persistant. Nociception induced by subplantar injection of formalin was also significantly attenuated by the essential oil at doses of 200 and 400 mg/kg. However, in a caudal compression test, a significant antinociceptive effect of the essential oil was observed only at 400 mg/kg. The antinociceptive effect of Psidium oil was not influenced by pretreatment of mice with naloxone (1 mg/kg, s. c.) in all the three tests. These observations suggest the presence of some volatile constituents in P. pohlianum essential oil capable of producing naloxone resistant antinociception in the mouse. Copyright © 1996 Gustav Fischer Verlag · Stuttgart · Jena · New York. Published by Elsevier GmbH.. All rights reserved.