The tramadol metabolite O-desmethyl tramadol inhibits substance P-receptor functions expressed in Xenopus oocytes.

Kouichiro Minami, Toru Yokoyama, Junichi Ogata, Yasuhito Uezono

Department of Anesthesiology and Critical Care Medicine, Jichi Medical University, Tochigi, Japan. kminami@med.uoeh-u.ac.jp

Journal of pharmacological sciences 2011

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Tramadol has been widely used as analgesic. O-Desmethyl tramadol (ODT) is one of the main metabolites of tramadol, having much greater analgesic potency than tramadol itself. Substance P receptors (SPR) are well known to modulate nociceptive transmission within the spinal cord. In this study, we investigated the effects of ODT on SPR expressed in Xenopus oocytes by examining SP-induced Ca(2+)-activated Cl(-) currents. ODT inhibited the SPR-induced Cl(-) currents at pharmacologically relevant concentrations. The protein kinase C (PKC) inhibitor bisindolylmaleimide I did not abolish the inhibitory effects of ODT on SP-induced Ca(2+)-activated Cl(-) currents. The results suggest that the tramadol metabolite ODT inhibits the SPR functions, which may be independent of activation of PKC-mediated pathways.

Citation

Kouichiro Minami, Toru Yokoyama, Junichi Ogata, Yasuhito Uezono. The tramadol metabolite O-desmethyl tramadol inhibits substance P-receptor functions expressed in Xenopus oocytes. Journal of pharmacological sciences. 2011;115(3):421-4