Geinisman Y, deToledo-Morrell L, Morrell F, Persina I S, Rossi M
Department of Cell, Molecular, Northwestern University Medical School, Chicago, IL 60611.
Hippocampus. 1992 Oct;2(4):445-56. doi: 10.1002/hipo.450020412.
Changes in synaptic numbers were examined in the hippocampal dentate gyrus of aged (28 months old) rats following the induction of long-term potentiation (LTP) by high-frequency stimulation of the medial perforant path carried out on each of 4 consecutive days. Potentiated animals were sacrificed 1 hour after the fourth stimulation. Stimulated but not potentiated and implanted but not stimulated rats of the same chronological age served as controls. Synapses were analyzed in the middle (MML) and inner (IML) molecular layer of the dentate gyrus. Using the stereological dissector technique, unbiased estimates of the number per neuron were obtained for the following morphological varieties of synapses: axodendritic synaptic junctions involving dendritic shafts, nonperforated axospinous synapses having a continuous postsynaptic density (PSD), and perforated ones distinguished by a fenestrated, horseshoe-shaped, or segmented PSD. The induction of LTP resulted in a selective increase in the number of synapses with segmented PSDs. This change was detected only in the potentiated synaptic field (MML), but not in an immediately adjacent one (IML), which was not directly stimulated during the induction of LTP. Comparison of these data with the results of our previous LTP study in young adult rats (Geinisman, Y. et al., 1991, Brain Res. 566:77-88) showed that the only significant difference in the absolute number of synaptic contacts per neuron between potentiated animals of the two chronological ages was an age-related reduction in segmented synapses of the MML. Relative increases in the number of segmented synapses per neuron were, however, virtually of the same magnitude in potentiated rats of both ages as compared with their respective controls. This finding may explain why senescent rats can be potentiated to the same extent as young ones.
连续4天每天对老年（28月龄）大鼠的内侧穿通路径进行高频刺激以诱导长时程增强（LTP），之后检测其海马齿状回中突触数量的变化。在第四次刺激后1小时处死增强组动物。将相同实际年龄的受刺激但未增强以及植入电极但未受刺激的大鼠作为对照。对齿状回的中层（MML）和内层（IML）分子层中的突触进行分析。使用体视学分割技术，对以下形态类型的突触获得了每个神经元数量的无偏估计：涉及树突干的轴突-树突突触连接、具有连续突触后致密物（PSD）的非穿孔轴突-棘突触，以及以有孔、马蹄形或分段PSD为特征的穿孔突触。LTP的诱导导致具有分段PSD的突触数量选择性增加。这种变化仅在增强的突触区域（MML）中检测到，而在紧邻区域（IML）中未检测到，后者在LTP诱导期间未直接受到刺激。将这些数据与我们之前在年轻成年大鼠中进行的LTP研究结果（Geinisman, Y.等人，1991年，《脑研究》566:77 - 88）进行比较，结果显示，两个实际年龄的增强组动物之间，每个神经元突触接触的绝对数量的唯一显著差异是MML中分段突触随年龄增长而减少。然而，与各自的对照组相比，两个年龄组的增强大鼠中每个神经元分段突触数量的相对增加幅度实际上是相同的。这一发现可能解释了为什么衰老的大鼠能够与年轻大鼠一样程度地被增强。
