Chen S, Hillman D E
Department of Physiology and Biophysics, New York University Medical Center, NY 10016.
Brain Res. 1990 Jun 18;520(1-2):103-14. doi: 10.1016/0006-8993(90)91695-d.
Partial ablation of the cerebral cortical input to the neostriatum generates a rapid lasting effect on the size of remaining synaptic sites. The neocortex was lesioned in adult rats and the neostriatum was analyzed for effects on remaining spines of principal cells during the period from 2 to 40 days. There was an increase in the size of spine heads, boutons and synaptic contact sites. The spine heads became very complex and a corresponding bouton enlargement was accompanied by an increase in the number of synaptic vesicles. By two days, the average profile length of postsynaptic membrane densities (PSDs) had increased by 25% representing an equivalent 50% increase in synaptic contact area. The number of synaptic sites was reduced on each principal neuron of the lesioned group. Comparison of the number of sites per unit volume to their average contact area revealed a reciprocal relationship indicating a conservation in the total synaptic contact area on each neuron. This effect was consistent for all postsurgical days. The lack of a significant return of synaptic number by 40 days indicates that axonal sprouting is not a major factor in neuronal plasticity in the adult striatum. The rapid increase in the size of spines, boutons and synaptic sites at remaining connections suggests that dendrites are the first to initiate the plasticity response in adult neurons through postsynaptic attachments and their corresponding receptor structure. The underlying mechanism of this plasticity may be through a conservation of macromolecules forming postsynaptic membrane specializations on target neurons. Remaining axons appear to follow the dendritic response with a plasticity generating presynaptic appositional specializations to match the contact area of the postsynaptic site.
对新纹状体的大脑皮质输入进行部分切除，会对剩余突触位点的大小产生快速且持久的影响。在成年大鼠中损伤新皮质，并在术后2至40天期间分析新纹状体对主要细胞剩余棘突的影响。棘突头部、轴突终扣和突触接触位点的大小均有所增加。棘突头部变得非常复杂，相应的轴突终扣增大伴随着突触小泡数量的增加。到术后两天，突触后膜致密物（PSD）的平均轮廓长度增加了25%，这意味着突触接触面积相应增加了50%。损伤组每个主要神经元上的突触位点数量减少。将单位体积内的突触位点数量与其平均接触面积进行比较，发现二者呈反比关系，这表明每个神经元上的总突触接触面积保持不变。在所有术后天数中，这种效应都是一致的。术后40天时突触数量没有显著恢复，这表明轴突发芽不是成年纹状体神经元可塑性的主要因素。剩余连接部位的棘突、轴突终扣和突触位点大小迅速增加，这表明树突是成年神经元通过突触后附着及其相应受体结构启动可塑性反应的首要部位。这种可塑性的潜在机制可能是通过在靶神经元上形成突触后膜特化的大分子的守恒来实现的。剩余的轴突似乎跟随树突的反应，产生突触前并置特化以匹配突触后位点的接触面积。
