Sasaki S, Maruyama S
Department of Neurology, Tokyo Women's Medical College, Japan.
Acta Neuropathol. 1994;88(3):222-7. doi: 10.1007/BF00293397.
This report deals with an ultrastructural investigation of the synapses of anterior horn neurons in the lumbar spinal cords of five patients with amyotrophic lateral sclerosis (ALS) who had mild neuronal depletion. Specimens from five age-matched, neurologically normal individuals served as controls. In each instance, the autopsy was performed within 3 h after death. A statistically significant decrease in cell body area, number of synapses and total synaptic length was found in the normal-appearing neurons of the ALS patients. The alterations were more pronounced in neurons with central chromatolysis. However, despite an approximately 20% reduction in the number of synapses, the length of the active synaptic zone of the normal-appearing neurons in the ALS patients was not diminished. This observation may be accounted for by a plasticity to the loss of synapses which maintained the active zone of the remaining synapses to increase synaptic efficiency. It is suggested that when the plasticity of the active zone reaches its limit, the continuing loss of synapses may lead to functional impairment. The capacity of the active synaptic zone to respond to progressive denervation of the anterior horn neurons may preserve motor function or slow the development of motor deficits in the early stage of degeneration of the lower motor neurons.
本报告对5例患有轻度神经元缺失的肌萎缩侧索硬化症（ALS）患者腰段脊髓前角神经元的突触进行了超微结构研究。选取5例年龄匹配、神经系统正常的个体作为对照。每例均在死后3小时内进行尸检。在ALS患者外观正常的神经元中，发现细胞体面积、突触数量和总突触长度有统计学意义的减少。这些改变在有中央性染色质溶解的神经元中更为明显。然而，尽管ALS患者外观正常的神经元突触数量减少了约20%，但其活性突触区的长度并未减少。这一观察结果可能是由于突触丢失后的可塑性，维持了剩余突触的活性区以提高突触效率。提示当活性区的可塑性达到极限时，突触的持续丢失可能导致功能障碍。活性突触区对前角神经元进行性失神经的反应能力可能在运动神经元变性早期保留运动功能或减缓运动功能缺损的发展。
