Tweedle C D, Smithson K G, Hatton G I
Department of Anatomy, Michigan State University, East Lansing 48824.
Exp Neurol. 1993 Dec;124(2):200-7. doi: 10.1006/exnr.1993.1190.
In the dendritic region of the supraoptic nucleus of young adult rats we found ultrastructural evidence of rapid (< 30 min) morphological reorganization following transcardial perfusion of the anesthetized animals with high (325 mOsm), but not with normal, osmolality (302 mOsm) balanced salt solutions. The changes observed included significant increases in dendritic bundling and increased numbers of multiple axodendritic synapses (where one presynaptic terminal contacted two or more postsynaptic dendrites). In our initial experiments the perfusion medium contained tannic acid, but when the tannic acid was omitted in a separate set of experiments, the results were both similar and more striking. These studies indicate that the plasticity previously seen in this region under physiological conditions can occur rapidly and probably involves astrocytic process withdrawal from between adjacent dendrites. This change in the distribution of astrocytic processes allows previously single synapses access to additional postsynaptic dendritic membrane. Together, increased dendritic bundling and multiple synapses may facilitate the synchronization of cell firing and, thus, hormone release.
在年轻成年大鼠视上核的树突区域，我们发现了超微结构证据，表明在对麻醉动物经心灌注高渗（325毫渗量）而非等渗（302毫渗量）平衡盐溶液后，树突会在短时间内（<30分钟）发生形态重组。观察到的变化包括树突束显著增加以及多个轴突 - 树突突触数量增多（即一个突触前终末与两个或更多突触后树突接触）。在我们最初的实验中，灌注介质含有单宁酸，但在另一组实验中去除单宁酸后，结果既相似又更显著。这些研究表明，此前在该区域生理条件下所见的可塑性能够迅速发生，并且可能涉及星形胶质细胞从相邻树突之间撤离其突起。星形胶质细胞突起分布的这种变化使先前单个突触能够接触到额外的突触后树突膜。树突束增加和多个突触共同作用，可能有助于细胞放电同步化，进而促进激素释放。
