Antinociceptive potential of <i>Parkia platycephala</i> Benth. in streptozotocin-induced diabetic rats

Abstract

This study aimed to investigate the possible antinociceptive action of the ethanolic extract (E.EtOH) and ethyl acetate fraction (F.AcOEt) from leaves of Parkia platycephala in streptozotocin (STZ)-induced diabetic rats. In chronic experiment, STZ-rats were daily treated with E.EtOH (150 or 300 mg/kg, p.o) for three weeks. The mechanical nociceptive threshold (MNT) was determined by application of von Frey filaments to the right hind paw before and 1, 2 and 3 weeks after diabetes induction. The STZ-E.EtOH 300 mg/kg group presented MNT higher than that in the STZ-vehicle group (untreated diabetic rats) at the third week. This effect was similar to the STZ-insulin group (6 U/rat/day), but did not reach the value of the control group (non-diabetic rats).  Although, E.EtOH 150 mg/kg had induced a decrease on serum glucose when compared with initial glucose, there was no significant difference between STZ-vehicle and E.EtOH-treated diabetic rats. In acute   experiments, untreated diabetic rats received F.AcOEt (6.25, 12.5, 50 and 150 mg/kg, p.o) at the third week of diabetes. F.AcOEt improved the tactile allodynia evaluated by MNT. Moreover, STZ-F.AcOEt 50 mg/kg presented antinociceptive effect in the late phase of formalin test. These findings indicate that E.EtOH and F.AcOEt showed analgesic actions in diabetic rats.

Key words: Parkia platycephala, diabetic neuropathy, tactile allodynia, formalin test, analgesic action.