Thesis (M.Sc.)--Chulalongkorn University, 2002

The crude extract of anacardium occidentale leaves (ANA) has been used in folk medicine for treating sore gums and toothache. In these studies, we initially determined the analgesic property of a range of ANA doses in the mouse hot-plate test. Hot-plate latencies (cut-off 45 sec) were determined prior to the intraperitoneal (i.p.) administration of 0.9% normal saline solution (NSS), morphine (MO: 10 mg/kg), acetylsalicylic acid (ASA: 150 mg/kg) of various doses of ANA (62.5, 125, 250, 500, 750, 1,000 mg/kg). Hot-plate latencies were subsequently determined at 15, 30, 45, 60, 90, 120, 240 min. The percent maximum possible effect (%MPE) was calculated and used in the determination of the area of analgesia (%MPE-min). ANA in doses of 125 mg/kg and higher produced a significant dose-related analgesic response. ANA (500 mg/kg) produced analgesic response that was naloxone-sensitive and attenuated by NMDA (0.38 mg/kg) suggesting opioid and NMDA-mediated mechanisms. In the mouse tail-flick analgesia test, tail-flick latencies (cut-off 4 sec) were determined in male ICR mice prior to the i.p. administration of NSS, MO, ASA or various doses of ANA (62.5-1,000 mg/kg) and subsequently determined at 7 intervals over a 4-hr period. All doses of ANA produced a dose-dependent analgesic response. Studies then determined the analgesic effect of ANA using the Randall-Selitto analgesia test. Paw-pressure latencies were determined in male Wistar rats prior to the i.p. administration of NSS, MO, ASA or various doses of ANA (62.5-1,000 mg/kg). Paw-pressure latencies were subsequently determined at 15, 30, 60, 90, 120, 240 min. ANA doses of 250 mg/kg and higher produced a significant dose-related analgesic response. Paw-pressure latencies were also determined in male Wister rats prior to the i.p. administration of NSS, MO, indomethacin (5 mg/kg) or various deses of ANA (62.5-1,000 mg/kg). Carrageenan was then administered into subplantar area of a right hind paw to induce inflammatory response. Withdrawal threshold were determined 2 hours after carrageenan administered on both inflamed and non-inflamed paw. ANA doses of 250 mg/kg and higher produced a significant dose-related antihyperalgesic activity. ANA doses of 125, 250, and 500 mg/kg i.p. failed to produce motor impairment compared to vehicle control in rota-rod test. Taken together these results demonstrate that the crude extract of anacardium occidentale leaves produced analgesic effect that was dose-dependent in all analgesic testing models without altered motor performance and mechanism of actions seem to be related to opioid receptor and partially involved NMDA receptor.