Voluntary exercise is sufficient to protect against neuropathic pain. However, it is unclear whether voluntary exercise reduces immobilization-induced hyperalgesia. We examined the effect of voluntary forelimb exercise on immobilized-induced hyperalgesia in hind paws of rats. Wistar rats were randomly divided into the (1) both hind limbs immobilized group (IM group), (2) immobilization and exercise with nonimmobilized fore limbs group (EX group), and (3) control group. In the IM and EX groups, the bilateral ankle joints of each rat were immobilized in full plantar flexion with a plaster cast for eight weeks. In the EX group, voluntary exercise using nonimmobilized forelimbs in the running wheel was administered during the immobilization period, while hind limbs were kept immobilized (60 min/day, 5 days/week). Mechanical hyperalgesia in the hind paw was measured using a digital von Frey device every week. To investigate the abnormality of primary sensory neurons and central sensitization, the number of calcitonin gene-related peptide-positive cells in the dorsal root ganglion and the expression level of calcitonin gene-related peptide in the spinal dorsal horn were analyzed by immunohistochemical staining. Immobilization-induced mechanical hyperalgesia was inhibited in the EX group compared to the IM group at three weeks after immobilization. In the EX group, the number of calcitonin gene-related peptide-positive cells in the dorsal root ganglion and the expression level of calcitonin gene-related peptide were significantly decreased compared to those in the IM group. Our results therefore suggest that voluntary forelimb exercise during hind limb immobilization partially reduces immobilization-induced hyperalgesia by suppressing that the plastic changes of the primary sensory nerves that excessively transmit pain and increased responsiveness of nociceptive neurons in the spinal dorsal horn.

中文翻译：

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自愿前肢运动减少大鼠后爪固定引起的机械痛觉过敏

自愿锻炼足以防止神经性疼痛。然而，尚不清楚自愿运动是否会减少固定引起的痛觉过敏。我们检查了自愿前肢运动对大鼠后爪固定诱导的痛觉过敏的影响。Wistar大鼠随机分为(1)双后肢固定组(IM组)、(2)前肢非固定运动组(EX组)、(3)对照组。在 IM 和 EX 组中，每只大鼠的双侧踝关节都用石膏模型固定在完全跖屈状态下八周。在 EX 组中，在固定期间使用非固定前肢在跑轮上进行自愿运动，而后肢保持固定（60 分钟/天，5 天/周）。每周使用数字 von Frey 设备测量后爪的机械痛觉过敏。为研究初级感觉神经元和中枢致敏的异常，采用免疫组化染色法分析脊髓背根神经节中降钙素基因相关肽阳性细胞的数量和脊髓背角中降钙素基因相关肽的表达水平。在固定后三周，与 IM 组相比，EX 组中固定引起的机械痛觉过敏受到抑制。EX组背根神经节中降钙素基因相关肽阳性细胞数和降钙素基因相关肽表达水平较IM组显着降低。