Hirofuji Shinji, Yokota Atsushi, Ohno Katsunori, Kinoshita Mitsuo, Neo Masashi
Department of Orthopedic Surgery, Osaka Medical College, 2-7, Daigaku-machi, Takatsuki, Osaka, 569-8686, Japan.
Muscle Nerve. 2014 Sep;50(3):425-30. doi: 10.1002/mus.24172. Epub 2014 May 14.
To elucidate the mechanism of functional recovery after gradual nerve-stretch injury, we used rats in which the femur length was increased by 15 mm at 1.5 mm/day.
We performed electrophysiology, mRNA analysis of tetrodotoxin-resistant voltage-gated sodium channels (TTX-R VGSCs) in dorsal root ganglia, and histology of unmyelinated sciatic nerve fibers and examined pain thresholds at 1, 10, 20, and 30 days after cessation of lengthening.
Electrophysiology revealed conduction block after cessation that recovered after 30 days. TTX-R VGSC levels decreased immediately after cessation but were restored after 10 (Nav1.9) or 20 (Nav1.8) days. Histology revealed that injured unmyelinated nerve fibers regenerate 30 days after cessation. Pain threshold decreased gradually during lengthening but had not recovered to the control group level after 30 days.
Early restoration of TTX-R VGSC mRNA in dorsal root ganglia preceded functional recovery of stretched nerves before regeneration of injured unmyelinated nerve fibers.
为阐明逐渐性神经拉伸损伤后功能恢复的机制，我们使用了股骨长度以每天1.5毫米的速度增加15毫米的大鼠。
我们进行了电生理学研究、背根神经节中对河豚毒素耐受的电压门控钠通道（TTX-R VGSCs）的mRNA分析、无髓鞘坐骨神经纤维的组织学检查，并在延长停止后的第1、10、20和30天检测了疼痛阈值。
电生理学显示延长停止后出现传导阻滞，30天后恢复。TTX-R VGSC水平在延长停止后立即下降，但在10天（Nav1.9）或20天（Nav1.8）后恢复。组织学显示，受伤的无髓鞘神经纤维在延长停止30天后再生。疼痛阈值在延长过程中逐渐降低，但30天后未恢复到对照组水平。
背根神经节中TTX-R VGSC mRNA的早期恢复先于拉伸神经的功能恢复，且早于受伤无髓鞘神经纤维的再生。
