ANALGESIC EFFECT OF THE HERBAL MEDICINE CATUAMA IN THERMAL AND CHEMICAL-MODELS OF NOCICEPTION IN MICE

The antinociceptive effect of the herbal medicine Catuama and the hydr oalcoholic extract (HE) of each plant present in this extract were inv estigated in chemical and thermal models of nociception in mice. The e xtract of Catuama (200 mg/kg, p.o.) caused time-dependent and long-las ting antinociception against acetic acid-induced writhing, formalin an d capsaicin-induced licking and also in the tail-flick and hot-plate a ssays. Its maximal analgesic effect was reached 6 h after its oral adm inistration and this effect lasted for at least 12 h. When given 6 h p rior to testing (100 and 200 mg/kg, p.o.), the extract elicited dose-r elated antinociception, but at 400 mg/kg, its analgesic effect was gre atly reduced. The antinociception caused by the extract of Catauma, li ke those produced by morphine, was largely antagonized by naloxone. Th e daily administration of the extract (200 mg/kg, p.o. for 4 days) or morphine (5 mg/kg, s.c. for 4 days) produced progressive tolerance, an effect which was reverted by naloxone (5 mg/kg, i.p.). In addition, t he Catuama extract showed cross-tolerance with morphine. The Catuama a ntinociception was not due to its non-specific effects such as muscle relaxation or sedation of animals, nor was it secondary to its antiinf lammatory property. When analysed separately the hydroalcoholic extrac t (IIE) obtained from Trichilia catigua, Paullinia cupana, Ptychopelat um olacoids, Zinziber officinalis (200 mg/kg, p.o., 6 h prior) all inh ibited acetic acid-induced pain (82% +/- 2%; 66% +/- 2%; 42% +/- 2% an d 30% +/- 4% of inhibition, respectively (p < 0.01). In the formalin t est the HE of P. olacoids; P. cupana; T. catigua and to a lesser exten t, Z. officinalis (200 mg/kg, p.o., 6 h prior) also inhibited both pha ses of formalin-induced pain (p < 0.01). Thus, antinociception caused by the Catuama extract seems to be dependent on the interaction of the several active principles present in these plants. The mechanisms und erlying the antinociception caused by extract of herbal medicine Catua ma is still not completely understood, but a significant number of the se effects are related to its interaction with the naloxone sensitive opioid system. Together, the results indicate that the herbal medicine Catuama may constitute a useful therapeutic agent for the treatment o f clinical pain. (C) 1997 by John Wiley & Sons, Ltd.