Antinociceptive effect of some Argentine medicinal species of Eupatorium

Eupatorium laevigatum, E. arnottianum and E. subhastatum, plants used in Ar gentine folk medicine for the treatment of inflammation and pain related pr oblems, were evaluated for analgesic activity. The infusions of these speci es (500 mg/kg, p.o.) produced a reduction in the number of stretches of 46. 6%, 41.5% and 35.6% respectively, in the acetic acid induced writhing test. This antinociceptive effect of the infusions was not reversed by pretreatm ent with naloxone, The infusions studied did not produce antinociceptive ef fects when assayed in the hot plate test. These results suggest that the an algesic activity is exerted by a mechanism unrelated to interaction with op ioid systems. Copyright (C) 2000 John Wiley & Sons.