Brief bursts of high-frequency stimulation produce two types of structural change in rat hippocampus.
Brief bursts of high-frequency stimulation produce two types of structural change in rat hippocampus.
复制标题
短暂的高频刺激会在大鼠海马体中产生两种类型的结构变化。
作者：
K. Lee;F. Schottler;M. Oliver;G. Lynch
1.电生理和电子显微镜技术被用来调查可能的结构修改与诱导海马结构的长时程突触增强。用Schaffer侧副连合投射方法刺激和记录麻醉大鼠头侧海马CA 3区至CA 1区的投射。2.在一组动物中，以100 s-1的频率重复刺激1 s（增强），而另一组以0.2 s-1刺激3 min（对照）。第一个范例产生了显着增加的突触后电位的强度，持续没有递减的15分钟期间的控制测试，而重复的低频激活突触传递没有检测到的影响。3.测试后，对大鼠进行灌注并准备进行电子显微镜检查。发现了记录微电极尖端附近的树突区，并测量了突触的数量以及神经元的各种成分的面积和长度。4.树突棘上的突触接触的数量在两组之间没有差异，但是在接受高频刺激的动物（增强组）中，树突轴上的突触发生率高出33%。5.在以下任何测量的平均尺寸中均未观察到统计学显著变化：1）接触树突棘的突触结的面积，2）树突棘的面积，3）树突棘柄的宽度，4）树突棘上的突触后密度（PSD）的长度，5）接触树突轴的突触结的面积，6）树突轴上的PSD的长度。6.然而，有明显的变化，动物内的方差和分布的树突棘措施。具体而言，在强化组中，1）树突棘面积，2）树突棘上PSD长度和3）棘柄宽度的变异系数降低。在强化组中，这些指标的动物内分布正偏的程度也降低。7.这样看来，短暂的高频脉冲刺激产生了两种截然不同的结构变化：1）轴突触数量明显增加，2）树突棘变异性减少。这些形态学效应的突触反应的长时程增强的可能关系进行了讨论。
1. Electrophysiological and electron-microscopic techniques were used to investigate possible structural modifications associated with the induction of long-term synaptic potentiation in the hippocampal formation. Stimulation and recording were carried out using the Schaffer collateral-commissural projections from field CA3 to field CA1 of the rostra1 hippocampus of anesthetized rats. 2. In one group of animals repetitive stimulation was administered at a frequency of 100 s-l for 1 s (potentiated), while another group was stimulated at 0.2 s-l for 3 min (control). The first paradigm produced a marked increase in the strength of the postsynaptic potentials, which persisted without decrement for the 15-min periods of control testing, while the repetitive low-frequency activation had no detectable effects on synaptic transmission. 3. Following testing, the rats were perfused and prepared for electron microscopy. The dendritic zone adjacent to the recording microelectrode tip was found and measurements made of the numbers of synapses as well as of the area and length of various constituents of the neuropil. 4. The number of synaptic contacts on dendritic spines was not different between the two groups, but the incidence of synapses onto dendritic shafts was 33% higher in the animals that received high-frequency stimulation (potentiated group). 5. No statistically significant changes were observed in the mean size of any of the following measures: 1) area of synaptic boutons contacting dendritic spines, 2) area of dendritic spines, 3) width of dendritic spine stalks, 4) length of postsynaptic densities (PSDs) on dendritic spines, 5) area of synaptic boutons contacting dendritic shafts, 6) length of PSDs on dendritic shafts. 6. However, there were distinct changes in the within-animal variance and distribution of the dendritic spine measures. Specifically, in the potentiated group there was a reduction in the coefficient of variation in 1) the area of dendritic spines, 2) the length of PSDs on dendritic spines, and3) the width of spine stalks. The extent to which the within-animal distributions of each of these measures were positively skewed was also reduced in the potentiated group. 7. It appears then that brief bursts of highfrequency stimulation produce two very different types of structural change: 1) an apparent increase in the number of shaft synapses, and 2) a decrease in the variability of the dendritic spines. The possible relationship of these morphological effects to long-term potentiation of synaptic responses is discussed.