anti-nociceptive activity of quebracho tannin extract on pain induced by formalin and writhing tests in mice

Background: based on positive role of the tannins for pain relief, there is no report for possible antinociceptive activity of the quebracho tannin.objectives: this study aimed to determine the anti-nociceptive activity of the quebracho tannin extract(qte) on pain in mice.materials and methods: for this purpose, 340 mice were used for formalin and writhing tests eachincluding 4 experiments with 4 sub-groups. in experiment 1, mice were injected with saline, qte(100 mg/kg), qte (200 mg/kg), qte (400 mg/kg), and morphine (5 mg/kg). in the second experiment,injections included saline, qte (400 mg/kg), naloxone (2 mg/kg), and qte + naloxone. experiments3 and 4 were similar to experiment 2, except that mice injected were with ng-nitro arginine methyl ester (l-name, 10 mg/kg) and cyproheptadine (4 mg/kg) instead of naloxone. then, formalin (1%) was injected, and time spent for licking the injected paw was recorded until 30 minutes following injection inthe first and second phases. finally, injections in 4 experiment groups were the same, and animals wereintraperitoneally injected with acetic acid, and contractions were recorded in the writhing test category.results: according to the results, qte (100, 200, and 400 mg/kg) decreased pain in the injected paw(p = 0.001) and inhibited the pain response by 59.37% (p = 0.001). moreover, the injection of naloxone +qte significantly decreased pain in the injected paw (p = 0.021). eventually, the injection of the l-name+ qte significantly reduced the anti-nociception effect of the qte on the formalin test (p = 0.031) andwrithing contractions (55.75%, p = 0.033).conclusion: these findings suggested anti-nociceptive properties of the qte mediated by opioidergicand nitrergic systems.