The peripheral antinociceptive effect of resveratrol is associated with activation of potassium channels

Abstract

The possible participation of K⁺ channels in the antinociceptive action induced by resveratrol was assessed in the 1% formalin test. Local administration of resveratrol produced a dose-dependent antinociception in the second phase of the test. The antinociception produced by resveratrol was due to a local action as its administration in the contralateral paw was not active. Local pretreatment of the injured paw with glibenclamide, tolbutamide or glipizide (ATP-sensitive K⁺ channel inhibitors) did not modify resveratrol-induced antinociception. In contrast, charybdotoxin and apamin (large and small conductance Ca²⁺ activated-K⁺ channel blockers, respectively), 4-aminopyridine or tetraethylammonium (voltage-dependent K⁺ channel inhibitors) dose-dependently prevented resveratrol-induced antinociception. Local peripheral administration of glibenclamide, but not charybdotoxin or apamin, significantly reduced the antinociceptive effect produced by peripheral morphine (positive control). At the highest effective doses, none of the drugs used induced behavioral side effects as revealed by the evaluation of stepping, righting, corneal and pinna reflexes. In addition, when given alone, none of the inhibitors modified the nociceptive behavior induced by 1% formalin. The results suggest that resveratrol opens large and small conductance Ca²⁺-activated K⁺ channels, but not ATP-sensitive K⁺ channels, in order to produce its peripheral antinociceptive effect in the formalin test. The participation of voltage-dependent K⁺ channels was also suggested, but since non-selective inhibitors were used the data awaits further confirmation.

Introduction

Resveratrol is a naturally occurring phytoalexin present in grapes and wine. The effects produced by this drug include inhibition of arachidonate metabolism in leukocytes and platelets (Kimura et al., 1995, Pace-Asciak et al., 1995), modulation of lipid metabolism, chelation of copper, inhibition of platelet aggregation, lipid peroxidation as well as vasorelaxing, anticancer and anti-inflammatory activity (for a review see Frémont, 2000). Resveratrol has been proposed to be a selective cyclooxygenase-1 (COX-1) inhibitor (Schwartz et al., 2000). However, other authors have reported that resveratrol inhibits the activity of COX-2 and suppresses the activation of COX-2 gene expression (Subbramaiah et al., 1998). There is also evidence that this drug reduces the release of inflammatory mediators by activated polymorphonuclear leukocytes (PMN) and down-regulates adhesion-dependent thrombogenic PMN functions (Rotondo et al., 1998). According to these actions, resveratrol is able to reverse hyperalgesia induced by tissue injury provoked by carrageenan or formalin injection in the rat paw (Gentilli et al., 2001, Torres-López et al., 2002).

Central K⁺ channels appear to be involved in the modulation of pain perception as intracerebroventricular administration of K⁺ channel openers produce antinociception in rats and mice (Narita et al., 1993), whereas intracerebroventricular K⁺ channel blockers reduce morphine-induced antinociception (Ocaña et al., 1990). The possible participation of K⁺ channels at the primary afferent neurons has been less studied. Recently, we have found that antinociception induced by some NSAIDs can be prevented by glibenclamide and other K⁺ channel inhibitors (Lázaro-Ibáñez et al., 2001, Ortiz et al., 2002), suggesting that these drugs could modulate K⁺ channels in order to produce their peripheral antinociceptive effect. Therefore, this work was undertaken to determine the possible participation of K⁺ channels on the peripheral antinociception induced by resveratrol. For this purpose, we tested the actions of glibenclamide, tolbutamide and glipizide (ATP-sensitive K⁺ channel blockers; Edwards and Weston, 1993), charybdotoxin (an inhibitor of large-conductance Ca²⁺-activated K⁺ channels; Stretton et al., 1992), apamin (an inhibitor of small-conductance Ca²⁺-activated K⁺ channels; Romey et al., 1984), 4-aminopyridine and tetraethylammonium (voltage-dependent K⁺ channel inhibitors; Cook and Quast, 1990) on resveratrol-induced antinociception in the 1% formalin test.