Experimental research to elucidate the pathogenesis and develop treatment for pain due to inactivity

为了阐明静止性疼痛的发病机制和治疗方法，我们建立了大鼠后肢固定模型，以评估机械刺激与疼痛的关系和影响。不活动引起的疼痛评估如下。行为学评价包括腓肠肌疼痛阈值测量和后足垫逃离反应次数测量。组织病理学评估包括测量腓肠肌坏死纤维的数量。分子生物学评价采用L4 -6脊髓背根神经节和背角标本进行RNA提取和实时聚合酶链反应。结果：固定后立即腓肠肌痛阈降低，后足垫逃避反应次数增加，但机械刺激干预组这些参数早期趋于正常化。组织病理学评估显示，与干预组相比，固定组有明显的肌肉损伤。此外，分子生物学评价显示，固定组大鼠背角脑组织中脑源性神经营养因子mRNA表达较高。这些发现表明，疼痛的发生是由于肌肉和皮肤的不活动，BDNF mRNA的表达在这种疼痛的发病机制中起作用。

As experimental research with the goal of elucidating the pathogenesis and developing treatments for pain due to inactivity, we created a rat model using cast immobilization of the hindlimbs to evaluate the relationship to pain and the influence of mechanical stimulation.Pain due to inactivity was evaluated as follows. Behavioral evaluation included measurement of painthresholds using the gastrocnemius muscle and measurement of the number of escape responses of hind foot pad. Histopathological evaluation included measuring the number of necrotic fibers in the gastrocnemius muscle. Molecular biological evaluation included RNA extraction and real-time polymerase chain reaction using specimens of the dorsal root ganglion and dorsal horn of the L4 -6 spinal cord.Results: A decreased pain threshold of gastrocunemius and increased number of escape responses of hind foot pad were observed immediately after immobilization, but these parameters tended to normalize early in the intervention group with mechanical stimulation. Histopathological evaluation showed marked muscle injury in the immobilization group compared to the intervention group. In addition, molecular biological evaluation showed higher expression of brain-derived neurotrophic factor mRNA in the dorsal horn in the immobilization group.These findings show that the development of pain is due to inactivity in both muscle and skin, and that BDNF mRNA expression plays a role in the pathogenesis of this pain.