ANALGESIC AND ANTIINFLAMMATORY ACTIVITIES OF AGERATUM CONYZOIDES IN RATS

The water soluble fraction (WSF) obtained from a hydroalcohol extract of A. conyzoides, a medicinal plant used in Brazilian folk medicine, w as evaluated for possible analgesic and antiinflammatory activities. I t was demonstrated that WSF (20-50 mg/kg; i.p.) treatment reduced the articular incapacitation induced by carrageenin (300 mu g) in rats, In this model, naloxone (2 mg/kg) blocked the analgesic action of morphi ne (2 mg/ kg) but did not change the WSF antinociceptive effect. It su ggests that endogenous opioids are not involved in the WSF antinocicep tive effect. The neutrophil migration induced by carrageenin (300 mu g ) injection into rat peritoneal cavities and into 6-day-old subcutaneo us air-pouches was significantly inhibited (p < 0.05) by WSF pretreatm ent (30 and 50 mg/kg; s.c.). At the same dose WSF also inhibited (p<0. 05) the carrageenin (400 mu g/paw)-induced oedema, but failed to modif y the oedema induced by dextran (100 mu g/paw). Furthermore, the incre ase in the cutaneous vascular permeability induced by the potent leuko cyte chemotactic agent LTB4 (39 ng co-injected with 500 ng iloprost, i .d.) was significantly blocked by WSF (30 mg/kg; i.p.). However, in th e same dose WSF caused a 2-fold increase in the vascular permeability induced by histamine (10 mu g), a direct vasoactive mediator. These re sults suggest that WSF can inhibit the inflammatory reactions induced by neutrophil mobilizing stimuli. (C) 1997 by John Wiley & Sons, Ltd.