Devor M, Govrin-Lippmann R, Frank I, Raber P
Somatosens Res. 1985;3(2):139-67. doi: 10.3109/07367228509144581.
This study was aimed at measuring the kinetics of retrograde death among primary sensory neurons axotomized by transection of the ipsilateral sciatic nerve in adult rats. Using electrophysiological and retrograde transport methods, we first determined that most sciatic afferents enter the spinal cord along the L4 and L5 dorsal roots (DRs), and that about 54% of the cells in the L4 and L5 dorsal root ganglia (DRGs) project an axon into the sciatic nerve. Knowing this value, we could then calculate the rate of loss of axotomized neurons from the overall rate of neuron loss in the DRGs at different times after the lesion. Following unilateral sciatic neurectomy, we found a steady falloff in the ratio of DRG neurons on the operated versus the intact control sides in cresyl-violet-stained serial paraffin sections. We were surprised to note, however, that on the control side there was a steady increase in the cell count with age. Counts done on a series of unoperated rats of various ages confirmed this natural increase. Overall, new neurons accrete at an average rate of 18.1 cells per day to the combined L4 and L5 DRGs, nearly doubling their numbers during the adult life of the animal. The new cells add mostly to the small-diameter neuronal compartment. Evidence from neonatally operated rats indicates that the decline in the ratio of neurons in operated versus control DRGs following sciatic nerve section in the adult results more from a halt in the accretion of new neurons to the sciatic compartment than from frank cell death. From our data, we calculate that the loss of axotomized neurons occurs at a rate of only about 8% per 100 postoperative days.
本研究旨在测定成年大鼠因同侧坐骨神经横断而轴突切断的初级感觉神经元逆行死亡的动力学。我们使用电生理和逆行运输方法，首先确定大多数坐骨神经传入纤维沿L4和L5背根进入脊髓，并且L4和L5背根神经节（DRG）中约54%的细胞将轴突投射到坐骨神经中。了解这一数值后，我们就可以根据损伤后不同时间DRG中神经元损失的总体速率来计算轴突切断神经元的损失速率。单侧坐骨神经切除术后，我们发现甲酚紫染色的连续石蜡切片中，手术侧与完整对照侧DRG神经元的比例持续下降。然而，我们惊讶地注意到，在对照侧，细胞计数随年龄稳步增加。对一系列不同年龄未手术大鼠的计数证实了这种自然增加。总体而言，新神经元以平均每天18.1个细胞的速率累积到L4和L5 DRG的总和中，在动物成年期内其数量几乎翻倍。新细胞主要增加到小直径神经元区室。新生期手术大鼠的证据表明，成年后坐骨神经切断后，手术侧与对照侧DRG中神经元比例的下降更多是由于坐骨神经区室新神经元累积停止，而非直接的细胞死亡。根据我们的数据，我们计算出轴突切断神经元的损失速率仅约为每术后100天8%。
