科研之友
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摘要
We investigated the effects of a non-specific sodium channel blocker (lidocaine) on heat pain thresholds and mechanical impact pain at day 7 and 21 after intradermal injection of 1 mu g NGF. Measurements were performed in 12 healthy male subjects prior to and 5 min after intradermal injection of 150 mu l lidocaine administered at concentrations of 0.01% (similar to 0.4 mM) and 0.1% (similar to 4 mM) to both NGF and control skin sites. NGF caused a maximum reduction of heat pain thresholds at day 7 (NGF 42.6 +/- 0.6 vs. 49.4 +/- 0.3 degrees C in control skin). Lidocaine sensitized normal skin for heat pain, but reduced heat hyperalgesia after NGF at day 7 (44.3 +/- 0.8 degrees C, lidocaine 0.1%; p < 0.005). Pain upon supra-threshold mechanical impact stimulation was increased after NGF at day 7 (VAS 29 + 5) and massively enhanced at day 21 (VAS 64 + 5, p < 0.001). Lidocaine dose-dependently attenuated mechanically-induced pain at both control and NGF-treated sites. Maximum lidocaine effects on mechanical hyperalgesia were recorded at day 21 in NGF skin (pain reduction to VAS 37 +/- 4, p < 0.00001). Repetitive impact stimuli caused increasingly more pain at the NGF sites at day 21 and this pain increase was efficiently suppressed by lidocaine 0.1%. Lidocaine differentially affects NGF-induced mechanical hyperalgesia (analgesic effect) and heat sensitivity of nociceptors (sensitizing effect). These opposing responses may be attributed to block of sodium channels vs. sensitization of TRPV1. NGF-evoked extreme mechanical impact pain indicates high action potential discharge frequencies, which might be more susceptible to lidocaine block.
- 出版日期2012-4
