Figure 1. Astrocytes play a critical role in supporting neurons in the CNS.

Astrocytes support neuronal functions in multiple ways. Indeed, the extracellular levels of ions and neurotransmitters can affect the excitability of neurons. (1) High concentrations of extracellular potassium can trigger the glycolysis of astrocytes, which can enhance the release of lactate and pyruvate, thereby supporting neuronal metabolism. (2) Astrocytes can take up glutamate and convert it to glutamine, which is then released into the extracellular space and taken up by neurons to resynthesize glutamate. Any deregulation of these mechanisms is a common condition for neurodegenerative diseases. (3) Under the circumstances of brain injury, disease or inflammatory insult, toxic proinflammatory mediators are secreted and released by astrocytes, which will act on neurons and may affect the survival of neurons.