Muscular Overuse Augments Spinal Cord Cross-over Serotoninergic Fibers during Recovery from Thoracic Spinal Cord Hemisection in Rats

先行研究によれば, ラットの胸髄が半切されると腰髄レベルでは脊髄交叉性にセロトニン線維が増加し, この影響により歩行運動機能の回復が促進されると考えられている。本研究の目的は, 脊髄交叉性のセロトニン線維の増加が半切側下肢を過用させることで影響されるかどうかを免疫組織化学的に検討することである。実験動物は6週齢のウィスター系雄ラットで, 胸髄右側を半切した31匹のうち18匹はそのまま回復させ, 13匹は半切側下肢を過用させる目的で対側坐骨神経を切断した。結果, 半切側の腰髄前角に分布するセロトニン線維は, 半切1週後は著名に減少したが, 2, 3週後には増加・再分布が認められ, これは半切側下肢を過用させた場合が著しかった。したがって, 脊髄交叉性のセロトニン線維の増加は, 半切側下肢の過用によって促進されると推察される。Spinal cord cross-over serotoninergic fibers increase when the thoracic spinal cord of a rat is hemisected and the recovery of locomotion is stimulated. The purpose of this study was to examine whether muscular overuse affects this increase in spinal cord cross-over serotoninergic fibers. Forty-four Wister male rats(6 weeks old)were divided into a control group(n=13)and an experimental group(n=31). All rats of the experimental group underwent right thoracic spinal cord hemisection(T8), and 18 of them were recovered with no other procedures. The other 13 rats in the experimental group were further underwent denervation of the contralateral left sciatic nerve to bring about a compensatory overuse on the ipsilateral right hindlimb. The rats were then sacrificed every week for 3 weeks after thoracic spinal cord hemisection. Distribution of the spinal cord cross-over serotoninergic fibers in the lumbosacral ventral horn was examined by immunohistochemical methods, and found to be more prevalent in the hemisected with the denervation of contralateral sciatic nerve than in the other hemisected rats. The results of this experiment suggest that the increase of the spinal cord cross-over serotoninergic fibers following thoracic spinal cord hemisection may be encouraged by overuse of the hindlimb