It has been demonstrated that the leguminous lectin isolated from Canavalia brasiliensis (ConBr), administered per oral to mice, exhibits peripheral and central antinociceptive effects mediated by the opioid system and the lectin domain. The objective of this study was to investigate the involvement of the correlated antinociceptive pathways, nitric oxide and adrenergic, in the oral effect of ConBr in the formalin test. Male Swiss mice were treated with ConBr (100 mg/kg; p.o.) before the formalin test in presence of the nitric oxide synthase substrate L-arginine (3.4 mmol/kg; i.p.), or the α1 adrenoceptor antagonist prazosin (0.4 µmol/kg; i.p.). Investigation of the L-arginine/NO pathway showed that the antinociceptive effect of ConBr (P1: 52.5 ± 4.18 s) was not altered by L-arginine (P1: 56.67 ± 9.33 s) in the first phase of the formalin test. However in the second phase the ConBr effect (P2: 73.5 ± 11.63 s) was partially inhibited by L-arginine (P2: 118.25 ± 11.08 s). Involvement of the adrenergic pathway showed that prazosin (P1: 71.16 ± 9.16 s; P2: 219.22 ± 15.92 s) did not alter the antinociceptive effect of ConBr in the first phase (P1: 57.88 ± 5.52 s), but blocked the lectin effect in the second phase (P2: 65.14 ± 8.13 s). In conclusion, ConBr administration per oral in mice elicits antinociceptive activity via L-arginine/NO and adrenergic pathways in the inflammatory phase of the formalin test.
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