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Role of NMDA receptor activation in serotonin agonist-induced air-stepping in paraplegic mice.

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  • Author(s): Guertin, P. A.
  • Source:
    Spinal Cord. Mar2004, Vol. 42 Issue 3, p185-190. 6p. 2 Diagrams, 1 Chart, 1 Graph.
  • Additional Information
    • Subject Terms:
    • Abstract:
      STUDY DESIGN:: Experimental laboratory investigation of the effects of serotonergic and glutamatergic drugs in early paraplegic mice. OBJECTIVES:: To examine whether NMDA and 5-HT receptors synergistically participate to generate basic stepping movements in paraplegic mice. SETTING:: Laval University Medical Center, Quebec, Canada. METHODS:: Adult mice completely spinalized at the low-thoracic level 1 week earlier were suspended in harnesses for experiments. Acute drug-induced effects were examined on hindlimb movements filmed with a digital video camera. Detailed kinematic analyses included stick diagrams reconstructions of hindlimb movements and analysis of bilateral coordination, angular excursion, stepping amplitude and frequency. RESULTS:: A single treatment with the 5-HT2 agonist quipazine (>0.7?mg/kg, i.p.) induced episodes of air-stepping movements in the hindlimbs of paraplegic mice. In contrast, injection of the glutamatergic agonist NMDA (1-45?mg/kg i.p.) failed to induce rhythmicity, although nonlocomotor rhythmic movements were observed with higher doses (45-60?mg/kg i.p.). Subthreshold doses of NMDA (22-30?mg/kg) could induce episodes of hindlimb air-stepping if combined with subthreshold doses of quipazine (0.3-0.7?mg/kg). Air-stepping was entirely blocked by administration of the selective NMDA antagonist MK-801. CONCLUSION:: A single treatment with quipazine can trigger episodes of locomotor-like movements in early chronic spinal mice. Even though NMDA alone could not generate bilaterally coordinated air-stepping, NMDA receptor activation was nonetheless critical for spinal locomotor rhythmogenesis induced by 5-HT agonists in awake behaving animals.Spinal Cord (2004) 42, 185-190. doi:10.1038/sj.sc.3101580 [ABSTRACT FROM AUTHOR]
    • Abstract:
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