Geinisman Y, Morrell F, deToledo-Morrell L
Department of Cell Biology and Anatomy, Northwestern University Medical School, Chicago, IL 60611.
Proc Natl Acad Sci U S A. 1988 May;85(9):3260-4. doi: 10.1073/pnas.85.9.3260.
The "kindling" phenomenon is associated with long-lasting facilitation of synaptic transmission. A possible mechanism of such facilitation could involve changes in the number of synaptic contacts. However, previous attempts to demonstrate a synaptic morphological alteration that could account for the long-term effects of kindling had failed, possibly due to the unavailability, at the time, of unbiased methods for synapse quantitation. Using the unbiased stereological disector technique, we estimated the number of synapses per neuron in the middle molecular layer of the hippocampal dentate gyrus in rats kindled by electrical stimulation of the medial perforant path with implanted electrodes. Unkindled but stimulated (coulombic control) and unstimulated but implanted rats served as controls. Animals were coded and killed 4 weeks after reaching the kindling criterion of five generalized seizures. The most important results were obtained when axospinous synapses with continuous or discontinuous postsynaptic densities ("nonperforated" or "perforated" synapses) were differentially analyzed. Kindling resulted in a selective loss of nonperforated synaptic contacts in contrast to preservation of perforated ones. Furthermore, the ratio of perforated to nonperforated synapses was increased by 45% or 40% in kindled rats relative to unstimulated or coulombic controls, respectively. These findings suggest that synaptic efficacy may depend on a balance of the two synaptic types; selective elimination of nonperforated synapses may augment the potency of remaining synaptic contacts, a process reminiscent of synaptic remodeling during development.
“点燃”现象与突触传递的长期易化有关。这种易化的一种可能机制可能涉及突触连接数量的变化。然而，先前试图证明一种能解释点燃长期效应的突触形态改变的尝试均告失败，这可能是因为当时缺乏无偏倚的突触定量方法。我们使用无偏倚的体视学分割技术，估计了通过植入电极电刺激内侧穿通路径点燃的大鼠海马齿状回中层分子层中每个神经元的突触数量。未点燃但接受刺激（库仑对照）的大鼠以及未接受刺激但植入电极的大鼠作为对照。动物在达到五次全身性惊厥的点燃标准后4周进行编码并处死。当对具有连续或不连续突触后致密物的轴棘突触（“非穿孔”或“穿孔”突触）进行差异分析时，获得了最重要的结果。与穿孔突触的保留形成对比的是，点燃导致非穿孔突触连接的选择性丧失。此外，与未刺激或库仑对照相比，点燃大鼠中穿孔突触与非穿孔突触的比例分别增加了45%或40%。这些发现表明，突触效能可能取决于两种突触类型的平衡；非穿孔突触的选择性消除可能会增强剩余突触连接的效能，这一过程让人联想到发育过程中的突触重塑。
