星形胶质细胞的选择性调控

CONCLUSION

During evolution, neurons have lost many essential metabolic pathways as they became

increasingly specialized and gained the ability to generate action potentials and communicate

by synaptic transmission. As a consequence, neurons in the adult brain depend on metabolic

support from surrounding astrocytes. For example, neurons do not express the mitochondrial

enzyme glutamine dehydrogenase and cannot produce the chief excitatory transmitter,

glutamate, which in the adult CNS mediates 70% of neurotransmission. Since glutamate does

not pass through the blood-brain-barrier, excitatory transmission heavily depends on glutamate

produced by astrocytes 33. Similarly, synapse formation requires multiple lipids, including

cholesterol, produced by astrocytes 47. It is clear that neuron survival in both the normal and

the diseased brain relies heavily on surrounding astrocytes. A striking example is ischemic

infarcts, in which neurons do not survive if neighboring astrocytes are lost. While large gaps

exist with regard to our understanding of how ischemia affects the supportive function of

astrocytes, it is likely that failure of glutamate uptake, K+ buffering, water homeostasis,

vascular control, etc, all contribute to the massive loss of neurons in focal stroke. A challenge

for the future is to develop experimental tools to manipulate and monitor dynamic changes in

the supportive function in ischemic astrocytes.NIH-PA Author Manuscript

NIH-PA Author Manuscript

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