NALOXONE-RESISTANT ANTINOCICEPTIVE ACTIVITY IN THE ESSENTIAL OIL OF PSIDIUM-POHLIANUM BERG

The antinociceptive activity of the essential oil from leaves of Psidi um pohlianum Berg (Myrtaceae) was evaluated in mice using three differ ent nociceptive tests, namely, formalin, low temperature hot-plate (51 +/- 1 degrees C) and caudal compression method. Oral administration o f Psidium oil (100, 200 and 400 mg/kg) produced a dose-related signifi cant antinociception in a hot-plate test, in a manner similar to morph ine but appeared more persistant;Nociception induced by subplantar inj ection of formalin was also significantly attenuated by the essential oil at doses of 200 and 400 mg/kg. However, in a caudal compression te st, a significant antinociceptive effect of the essential oil was obse rved 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 som e volatile constituents in P. pohlianum essential oil capable of produ cing naloxone resistant antinociception in the mouse.