Contribution of nitric oxide, monoaminergic and opioidergic systems to the antinociceptive effects of tramadol and clonidine in rats and mice

ABSTRACT

In this study, thermal and chemical stimuli using hot plate and acetic acid tests were used. Tramadol hydrochloride produced antinociception in both hot plate test in rats and acetic acid analysis in mouse. The antinociceptive activity of tramadol was abolished by naloxone. Administration of yohimbine also reduced antinociception produced by administration of tramadol. These results suggested that tramadol- induced antinociception might be mediated by opioid and non-opioid mechanisms. Clonidine produced dose dependent antinociception using hot plate test. It was concluded that opioid receptors, alpha 2-adrenergic receptors and nitric oxide might play a role in pain transmission