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KMID : 0948320060060010001
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Konyang Medical Journal
2006 Volume.6 No. 1 p.1 ~ p.6
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Adenosine Receptor Antagonist Inhibits the Maintenance,and but not Induction,of Spinal Cord Stimulation Effect
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Kim Dong-Kwan
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Abstract
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Although the classical analgesic method is not efficient for the treatment of neuropathic pain, spinal cord stimulation (SCS) sometimes provides efficient pain relief. The antinociceptive effect of SCS in neuropathic pain state may be associated with GABA, adenosine or other neurotransmitter. However, there has not been regarding the relationship of fiber-specific activity with neurohumoral factor in neuropathic pain (NPP). In present study, we investigated whether adenosine A1 receptor is involved in the effects of SCS in neuropathic pain. In order to make NPP model animal, we performed the selective spinal nerve (L5/6) ligation (SNL) in adult rats (250 g). Animals developed mechanical and thermal allodynia in the operated paw. The effects of SCS (50 Hz, 0.2 ms, 20 mins) on the widedynamic range (WDR) neurons of NPP model rats were studied with single-unit extracellular recording 17-28 days after surgery. In the majority of WDR neurons, the application of SCS inhibited C-fiber activity of WDR neurons, whereas the effects on A-fiber activities were not statistically significant. Local administration, iontophoretic injection (aminophylline 25 mg/ml), of an adenosine receptor antagonist reversed the antinociceptive effect of SCS on C-fiber activity. The same effects were reproduced by DPCPX, a selective adenosine A1 receptor antagonist. However, the same dose of aminophylline during SCS did not block the induction of suppressive effect by SCS. These results indicate that C-fiber evoked responses are inhibited in preference to A-fiber evoked responses by SCS, and the activation of adenosine receptors is not necessary for the induction of SCS-mediated change in C-fiber-evoked action potentials in dorsal horn neurons. The mechanism underlined on the maintenance for antinociceptive effect of SCS may be associated with adenosine A1 receptor in NPP model rats.
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KEYWORD
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Neuropathic pain, Spinal cord stimulation, Adenosine A1 receptor, Dorsal horn neuron, Antinociceptive
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