Lidierth Malcolm
King's College London, Hodgkin Building, Guy's Campus, London SE1 1UL, United Kingdom.
Neurosci Lett. 2007 Sep 25;425(2):126-30. doi: 10.1016/j.neulet.2007.08.029. Epub 2007 Aug 19.
Electrical microstimulation has been used to activate fine myelinated primary afferents running within the Lissauer tract. Stimulation of the tract at the L2/L3 border produced antidromic volleys which were recorded on the dorsal roots of more caudal spinal segments. Antidromic volleys were present in all cases for roots as far caudal as the S2 segment (L3, n=12; L4, n=6; L5, n=6; L6, n=9; S1, n=3; S2, n=6; observations in a total of 15 rats). These fibres were collaterals of primary afferents with conduction velocities in the dorsal root of up to 17.3+/-2.3 ms(-1) (mean+/-S.D., n=6; range 14-20 ms(-1)). Conduction velocities within the Lissauer tract were slower; the fastest contributing fibres had conduction velocities of 9.2+/-2.2 ms(-1) (range 6-12 ms(-1)). Lesions of the Lissauer tract caudal to the stimulation site abolished the volleys on roots lying caudal to the lesion. Most previous works have suggested that primary afferents project in the Lissauer tract for only one or two spinal segments. The present study shows that some fibres project rostrally for up to seven spinal segments (L2-S2).
电微刺激已被用于激活在脊髓背外侧束内运行的有髓鞘的初级传入纤维。在L2/L3边界刺激该束会产生逆向冲动，这些冲动在更靠尾侧的脊髓节段的背根上被记录下来。在所有情况下，直至S2节段的背根都存在逆向冲动（L3，n = 12；L4，n = 6；L5，n = 6；L6，n = 9；S1，n = 3；S2，n = 6；总共对15只大鼠进行了观察）。这些纤维是初级传入纤维的侧支，其在背根中的传导速度高达17.3±2.3毫秒⁻¹（平均值±标准差，n = 6；范围为14 - 20毫秒⁻¹）。在脊髓背外侧束内的传导速度较慢；最快的相关纤维的传导速度为9.2±2.2毫秒⁻¹（范围为6 - 12毫秒⁻¹）。在刺激部位尾侧的脊髓背外侧束损伤消除了损伤尾侧背根上的冲动。以前的大多数研究表明，初级传入纤维在脊髓背外侧束中仅投射一两个脊髓节段。本研究表明，一些纤维向前投射多达七个脊髓节段（L2 - S2）。
