Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 104, Issue 20, Pages 8520-8525Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0611364104
Keywords
allodynia; electrophysiology; hyperalgesia; sensory neurons
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Activation of tetroclotoxin-resistant sodium channels contributes to action potential electrogenesis in neurons. Antisense oligonucleotide studies directed against Na(v)1.8 have shown that this channel contributes to experimental inflammatory and neuropathic pain. We report here the discovery of A-803467, a sodium channel blocker that potently blocks tetroclotoxin-resistant currents (IC50 = 140 nM) and the generation of spontaneous and electrically evoked action potentials in vitro in rat dorsal root ganglion neurons. In recombinant cell lines, A-803467 potently blocked human Na(v)1.8 (IC50 = 8 nM) and was > 100-fold selective vs. human Na(v)1.2, Na(v)1.3, Na(v)1.5, and Na(v)1.7 (IC50 values >= 1 mu M). A-803467 (20 mg/kg, i.v.) blocked mechanically evoked firing of wide dynamic range neurons in the rat spinal dorsal horn. A-803467 also dose-dependently reduced mechanical allodynia in a variety of rat pain models including: spinal nerve ligation (ED50 = 47 mg/kg, i.p.), sciatic nerve injury (ED50 = 85 mg/kg, i.p.), capsaicin-induced secondary mechanical allodynia (ED50 approximate to 100 mg/kg, i.p.), and thermal hyperalgesia after intraplantar complete Freund's adjuvant injection (ED50 = 41 mg/kg, i.p.). A-803467 was inactive against formalin-induced nociception and acute thermal and postoperative pain. These data demonstrate that acute and selective pharmacological blockade of Na(v)1.8 sodium channels in vivo produces significant antinociception in animal models of neuropathic and inflammatory pain.
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