Oliet S H R, Piet R
Inserm U378, Institut François Magendie, Université Victor Segalen, Bordeaux, France.
J Neuroendocrinol. 2004 Apr;16(4):303-7. doi: 10.1111/j.0953-8194.2004.01159.x.
The adult hypothalamic-neurohypophysial system undergoes activity-dependent morphological plasticity that modifies the astrocytic enwrapping of its magnocellular neurones. For a long time, the functional consequences of such changes have remained hypothetical. Modifications in the glial environment of neurones are expected to have important physiological repercussions in view of the various functions played by astrocytes in the central nervous system. In particular, glial cells are essential for uptake of neurotransmitters, including glutamate, and for physically and functionally restricting diffusion of neuroactive substances within the extracellular space. Recent studies performed in the supraoptic nucleus of lactating and chronically dehydrated animals, in conditions where astrocytic coverage of neurones is reduced, have revealed a significant impairment of glutamate clearance. The resulting accumulation of the excitatory amino acid in the extracellular space around glutamatergic inputs causes an enhanced activation of presynaptic metabotropic glutamate receptors that inhibit transmitter release. In the supraoptic nucleus of lactating rats, neuroglial remodelling is accompanied by modification of the geometry, size and diffusion properties of the extracellular space. The latter observations suggest that, in the activated supraoptic nucleus, the range of action and the concentration of released neuroactive substances may be significantly enhanced. Overall, our observations indicate that the glial environment of supraoptic neurones influences synaptic glutamatergic transmission, as well as extrasynaptic forms of communication.
成年下丘脑 - 神经垂体系统会经历依赖活动的形态可塑性变化，这种变化会改变其大细胞神经元的星形胶质细胞包裹情况。长期以来，这种变化的功能后果一直停留在假设阶段。鉴于星形胶质细胞在中枢神经系统中发挥的多种功能，神经元胶质环境的改变预计会产生重要的生理影响。特别是，胶质细胞对于包括谷氨酸在内的神经递质的摄取至关重要，并且在物理和功能上限制神经活性物质在细胞外空间的扩散。最近在泌乳和长期脱水动物的视上核中进行的研究发现，在神经元的星形胶质细胞覆盖减少的情况下，谷氨酸清除存在显著受损。兴奋性氨基酸在谷氨酸能输入周围的细胞外空间中积累，导致突触前代谢型谷氨酸受体的激活增强，从而抑制递质释放。在泌乳大鼠的视上核中，神经胶质重塑伴随着细胞外空间几何形状、大小和扩散特性的改变。后一项观察结果表明，在激活的视上核中，释放的神经活性物质的作用范围和浓度可能会显著增加。总体而言，我们的观察结果表明，视上神经元的胶质环境会影响突触谷氨酸能传递以及突触外形式的通讯。
