伸張性収縮負荷2日後の機械痛覚過敏状態の筋からの機械刺激によるATP遊離 ATP release induced by the mechanical stimulation from the mechanically hyperalgesic muscle 2 days after lengthening contraction

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Author(s)

    • 田口 徹 Taguchi Toru
    • 名古屋大・環医研・神経系分野 Dept. Neusoceinece II, Res. Inst. Environ. Med., Nagoya Univ. Japan

Abstract

ATP is known to be released from injured or inflamed tissues, and to excite/sensitize nociceptors to heat and possibly to mechanical stimulation. We have reported that the extensor digitorum longus (EDL) muscle of rats 2 days after lengthening contraction (LC) is mechanically hyperalgesic and that the C-fiber receptors recorded from this hyperalgesic muscle have facilitated sensitivity to mechanical stimulation. To examine the possibility that this facilitated mechanical sensitivity is mediated by ATP released from the muscle, we measured ATP release from the muscle upon mechanical stimulation. Rats underwent LC of flexor muscle (mainly, EDL muscle) of the lower hindleg under anesthesia. Two days later, EDL muscle was excised under anesthesia and superfused with Krebs-Henseleit solution. The superfusate was sampled at 0.8 ml/min and its ATP concentration was measured with Luciferin-Luciferase method. At first we examined ATP release to repetitive application of 20 g force/10 s stimulation, which was used for the study of nociceptor characteristics, with a servo-controlled mechanical stimulator with intervals of 30 min. ATP release was clearly decreased on repetition of the mechanical stimulus. Then we examined stimulus response relationship by stimulating the muscle five times at 5, 10, 20 and 40 g forces at a rate of 10 g/s. ATP release was increased roughly stimulus-strength dependently in this range. Disappointingly, these results were not different from our previous results on normal unexercised muscles. <b>[J Physiol Sci. 2007;57 Suppl:S194]</b>

ATP is known to be released from injured or inflamed tissues, and to excite/sensitize nociceptors to heat and possibly to mechanical stimulation. We have reported that the extensor digitorum longus (EDL) muscle of rats 2 days after lengthening contraction (LC) is mechanically hyperalgesic and that the C-fiber receptors recorded from this hyperalgesic muscle have facilitated sensitivity to mechanical stimulation. To examine the possibility that this facilitated mechanical sensitivity is mediated by ATP released from the muscle, we measured ATP release from the muscle upon mechanical stimulation. Rats underwent LC of flexor muscle (mainly, EDL muscle) of the lower hindleg under anesthesia. Two days later, EDL muscle was excised under anesthesia and superfused with Krebs-Henseleit solution. The superfusate was sampled at 0.8 ml/min and its ATP concentration was measured with Luciferin-Luciferase method. At first we examined ATP release to repetitive application of 20 g force/10 s stimulation, which was used for the study of nociceptor characteristics, with a servo-controlled mechanical stimulator with intervals of 30 min. ATP release was clearly decreased on repetition of the mechanical stimulus. Then we examined stimulus response relationship by stimulating the muscle five times at 5, 10, 20 and 40 g forces at a rate of 10 g/s. ATP release was increased roughly stimulus-strength dependently in this range. Disappointingly, these results were not different from our previous results on normal unexercised muscles. <b>[J Physiol Sci. 2007;57 Suppl:S194]</b>

Journal

  • Proceedings of Annual Meeting of the Physiological Society of Japan

    Proceedings of Annual Meeting of the Physiological Society of Japan 2007(0), 194-194, 2007

    PHYSIOLOGICAL SOCIETY OF JAPAN

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