Shao Y, McCarthy K D
Department of Pharmacology, University of North Carolina at Chapel Hill 27599-7365.
Glia. 1994 Jun;11(2):147-55. doi: 10.1002/glia.440110209.
It is becoming apparent that astrocytes carry out a large number of different functions in brain and are able to modify their characteristics throughout life, that is they exhibit a high degree of plasticity in their phenotype. For example, the morphology of astrocytes changes markedly during neuronal migration, maturation, and degeneration. It is conceivable that these cells must constantly adjust their abilities to meet changes in brain environment. Several examples of astrocytic plasticity are presented in this review. First, the ability of astrocytes to recognize neuronal signals can change qualitatively as well as quantitatively; evidence suggests that the expression of glial receptors may be developmentally regulated by both intrinsic and extrinsic signals. Second, the expression of adrenergic receptors by astrocytes in adult brain can change in response to neuronal degeneration. The up-regulation of beta-adrenergic receptors in this case suggests that these receptors play a role in function of reactive astrocytes. Finally, glial morphology can be reciprocally regulated by neurotransmitters such as norepinephrine and glutamate. This reciprocal regulation may be significant since both beta-adrenergic receptors and glutamate transporters are found predominantly in astrocytes in the brain. The change in glial morphology may also affect neuronal activity by changing the volume of the extracellular space.
越来越明显的是，星形胶质细胞在大脑中执行大量不同的功能，并且能够在整个生命过程中改变其特性，也就是说它们在表型上表现出高度的可塑性。例如，在神经元迁移、成熟和退化过程中，星形胶质细胞的形态会发生显著变化。可以想象，这些细胞必须不断调整其能力以适应大脑环境的变化。本综述列举了星形胶质细胞可塑性的几个例子。首先，星形胶质细胞识别神经元信号的能力在质量和数量上都可能发生变化；有证据表明，胶质受体的表达可能受内在和外在信号的发育调控。其次，成年大脑中星形胶质细胞肾上腺素能受体的表达可因神经元退化而改变。在这种情况下，β-肾上腺素能受体的上调表明这些受体在反应性星形胶质细胞的功能中发挥作用。最后，胶质细胞形态可由去甲肾上腺素和谷氨酸等神经递质相互调节。这种相互调节可能很重要，因为β-肾上腺素能受体和谷氨酸转运体主要存在于大脑中的星形胶质细胞中。胶质细胞形态的变化也可能通过改变细胞外空间的体积来影响神经元活动。
