Theodosis D T, Poulain D A
Neurobiologie Morphofonctionnelle INSERM U. 378 Institute François Magendie, Bordeaux, France.
Adv Exp Med Biol. 1999;468:175-82. doi: 10.1007/978-1-4615-4685-6_14.
A striking example of the capacity of adult astrocytes to undergo reversible morphological changes in response to stimuli which enhance neuronal activity is offered by astrocytes of the adult hypothalamo-neurohypophysial system (HNS). The HNS is composed of magnocellular neurons secreting the neurohormones oxytocin and vasopressin from axon terminals in the neurohypophysis. Upon activation of HNS secretion, glial coverage of oxytocin neurons significantly diminishes and their surfaces become extensively juxtaposed. These glial changes are invariably accompanied by structural synaptic remodelling resulting in increased numbers of GABAergic, glutamatergic, and noradrenergic afferents. In the neurohypophysis, they result in an enhanced neurohemal contact area. HNS glia in the adult continue to display "embryonic" features that may allow such activity-dependent structural plasticity. For example, supraoptic astrocytes display a radial glia-like morphology and continue to express vimentin, together with GFAP. All HNS astrocytes secrete extracellular matrix glycoproteins, like tenascin-C; they also express high levels of polysialylated NCAM or PSA-NCAM and the glycoprotein F3, molecules considered essential for neuronal-glial interactions in the developing and lesioned CNS. HNS expression of most of these proteins does not visibly vary under different conditions of neurohormone secretion. We consider them as permissive factors, therefore, allowing HNS cells to undergo remodeling whenever the proper stimuli intervene. In the hypothalamic nuclei, one such stimulus is oxytocin itself which, in synergy with steroids, can induce neuronal-glial remodelling; adrenaline does so in the neurohypophysis.
成年下丘脑 - 神经垂体系统（HNS）的星形胶质细胞为成年星形胶质细胞响应增强神经元活动的刺激而发生可逆形态变化的能力提供了一个显著例子。HNS由大细胞神经元组成，这些神经元从神经垂体的轴突末端分泌神经激素催产素和加压素。在HNS分泌激活后，催产素神经元的胶质覆盖显著减少，其表面广泛并列。这些胶质变化总是伴随着结构性突触重塑，导致GABA能、谷氨酸能和去甲肾上腺素能传入神经数量增加。在神经垂体中，它们导致神经血接触面积增加。成年HNS中的胶质细胞继续表现出“胚胎”特征，这可能允许这种依赖活动的结构可塑性。例如，视上核星形胶质细胞呈现放射状胶质细胞样形态，并继续表达波形蛋白以及胶质纤维酸性蛋白（GFAP）。所有HNS星形胶质细胞都分泌细胞外基质糖蛋白，如腱生蛋白 - C；它们还高水平表达多唾液酸化神经细胞黏附分子（PSA - NCAM）和糖蛋白F3，这些分子被认为是发育中和受损中枢神经系统中神经元 - 胶质细胞相互作用所必需的。在不同神经激素分泌条件下，HNS中大多数这些蛋白质的表达没有明显变化。因此，我们认为它们是许可因子，允许HNS细胞在适当刺激介入时进行重塑。在下丘脑核中，一种这样的刺激是催产素本身，它与类固醇协同作用可诱导神经元 - 胶质细胞重塑；肾上腺素在神经垂体中起这样的作用。
