Resumo

Objectives: Determination of antinociceptive and anti-inflammatory properties of an unusual glucomannan (GM) isolated from the thallus of the lichenized fungus Heterodermia obscurata. Methods: Animals (Swiss mice of both sexes, 25-35g; N=6-8) were treated with GM (10-100 mg/kg) by intraperitoneal (i.p.) route. The antinociceptive activity was evaluated through an intraplantar (i.pl.) injection of glutamate (20µmol; 15min) and formalin (2,5%; first phase: 0-5min, second phase: 15-30min), and the time spent licking the injected paw was recorded. To evaluate the effect of GM against chronic model of nociception, mice were submitted to a parcial nerve ligation (PNSL) analyzed through Von Frey filaments (Up&Down method), and treated with GM, acutely and chronically. Additionally, the possible sedative or muscle-relaxant effect of GM was assessed on the Rota Rod and Open Field tests. All the experiments were approved by the Institutional Ethics Committee under the protocol PP00434. Results: GM, given via i.p., inhibited in a dose-dependent manner the glutamate- and first and second phases of formalin-induced nociception, with inhibitions of 85+5%, 65+5% with ID50 value of 70.66 mg/ kg (55.90 - 89.33), 98 + 2%, respectively. Moreover, GM (100 mg/kg) was able to reverse the PNSL-induced allodynia (C=0.71+0.06, GM 100 mg/kg=1.2+0.18). In addition, GM treatment affected the locomotor activity in Open Field test (C= 107+8.1 ; GM 100 mg/kg=35+7.4), but not at Rota Rod . Conclusions: Together, these results demonstrated that GM presents significant antinociceptive effect against acute and chronic pain, and also anti-inflamatory effect assessed on the second phase of formalin-induced nociception, and although some inespecific effect was observed in Open field test, the treatment did not presented muscle-relaxant effect, as assessed in Rota Rod apparatus.