BACKGROUND: It has been reported that curcumin, the main active compound of Curcuma longa, also known as turmeric, exhibits antinociceptive properties. The aim of this study was to examine the participation of ATP-sensitive potassium channels (KATP channels) and, in particular, that of the L-arginine-nitric oxide-cyclic GMP-KATP channel pathway, in the antinociceptive effect of curcumin. METHODS: Pain was induced by the intraplantar injection of 1% formalin in the right hind paw of Wistar rats. Formalin-induced flinching behavior was interpreted as an expression of nociception. The antinociceptive effect of oral curcumin was explored in the presence and absence of local pretreatment with L-NAME, an inhibitor of nitric oxide synthase, ODQ, an inhibitor of soluble guanylyl cyclase, and glibenclamide, a blocker of KATP channels. RESULTS: Oral curcumin produced a dose-dependent antinociceptive effect in the 1% formalin test. Curcumin-induced antinociception was not altered by local L-NAME or ODQ, but was significantly impaired by glibenclamide. CONCLUSIONS: Our results confirm that curcumin is an effective antinociceptive agent. Curcumin-induced antinociception appears to involve the participation of KATP channels at the peripheral level, as local injection of glibenclamide prevented its effect. Activation of KATP channels, however, does not occur by activation of the L-arginine-nitric oxide-cGMP-KATP channel pathway.
Curcuma ; Curcumin ; Formaldehyde ; Glyburide ; Guanylate Cyclase ; KATP Channels ; NG-Nitroarginine Methyl Ester ; Nitric Oxide Synthase ; Nociception ; Pain Measurement ; Potassium Channels ; Rats, Wistar ; Receptors, Cytoplasmic and Nuclear