Langle Sarah L, Poulain Dominique A, Theodosis Dionysia T
INSERM U378 Neuroendocrinologie Morphofonctionelle, Institut François Magendie, 1 Rue Camille Saint-Saëns, F33077 Bordeaux Cedex, France.
J Physiol Paris. 2002 Apr-Jun;96(3-4):169-75. doi: 10.1016/s0928-4257(02)00003-7.
Increasing evidence is establishing that adult neurons and their associated glia can undergo state-dependent changes in their morphology and in consequence, in their relationships and functional interactions. A neuronal system that illustrates this kind of neuronal-glial plasticity in an exemplary fashion is that responsible for the secretion of the neurohormone oxytocin (OT). As shown by comparative ultrastructural analysis, during physiological conditions like lactation and dehydration, which result in enhanced peripheral and central release of the peptide, astrocytic coverage of OT neurons is markedly reduced and their surfaces are left directly juxtaposed. Such reduced glial coverage is of consequence to neuronal activity since it modifies extracellular ionic homeostasis and glutamate neurotransmission. In addition, it is probably prerequisite to the synaptic remodeling that occurs concurrently, and results in an enhanced number of inhibitory (GABAergic) and excitatory (glutamatergic, noradrenergic) synapses, thus further affecting neuronal function. The neuronal-glial and synaptic changes occur rapidly, within a matter of hours, and are reversible with termination of stimulation. The adult OT system retains many juvenile molecular features that may allow such plasticity, including expression of cell adhesion molecules implicated in neuronal-glial interactions during development, like polysialylated NCAM, F3/contactin and its ligand, the matrix glycoprotein, tenascin-C. On the other hand, OT itself can induce the changes since in vivo (ventricular microinfusion) or in vitro (on acute hypothalamic slices) application leads to glial and neuronal transformations similar to those induced by physiological stimuli.
越来越多的证据表明，成年神经元及其相关的神经胶质细胞在形态上会发生状态依赖性变化，进而导致它们之间的关系和功能相互作用发生改变。一个以典型方式展示这种神经元 - 神经胶质可塑性的神经元系统是负责分泌神经激素催产素（OT）的系统。比较超微结构分析表明，在泌乳和脱水等生理条件下，这些条件会导致该肽在周围和中枢的释放增加，OT神经元的星形胶质细胞覆盖明显减少，其表面直接相邻。这种减少的胶质细胞覆盖对神经元活动有影响，因为它改变了细胞外离子稳态和谷氨酸神经传递。此外，它可能是同时发生的突触重塑的先决条件，突触重塑会导致抑制性（GABA能）和兴奋性（谷氨酸能、去甲肾上腺素能）突触数量增加，从而进一步影响神经元功能。神经元 - 神经胶质和突触变化在数小时内迅速发生，并且在刺激终止后是可逆的。成年OT系统保留了许多可能允许这种可塑性的幼年分子特征，包括在发育过程中参与神经元 - 神经胶质相互作用的细胞粘附分子的表达，如多唾液酸NCAM、F3/接触蛋白及其配体、基质糖蛋白腱生蛋白 - C。另一方面，OT本身可以诱导这些变化，因为在体内（脑室微量注射）或体外（在急性下丘脑切片上）应用会导致与生理刺激诱导的类似的胶质和神经元转变。
