The active role of astrocytes in synaptic transmission.
In the central nervous system, astrocytes form an intimately connected network with neurons, and their processes closely enwrap synapses. The critical role of these cells in metabolic and trophic support to neurons, ion buffering and clearance of neurotransmitters is well established. However, recent accumulating evidence suggests that astrocytes are active partners of neurons in additional and more complex functions. In particular, astrocytes express a repertoire of neurotransmitter receptors mirroring that of neighbouring synapses. Such receptors are stimulated during synaptic activity and start calcium signalling into the astrocyte network. Intracellular oscillations and intercellular calcium waves represent the astrocyte's own form of excitability, as they trigger release of transmitter (i.e. glutamate) via a novel process sensitive to blockers of exocytosis and involving cyclooxygenase eicosanoids. Astrocyte-released glutamate activates receptors on the surrounding neurons and modifies their electrical and intracellular calcium ([Ca2+]i) state. These exciting new findings reveal an active participation of astrocytes in synaptic transmission and the involvement of neuronastrocyte circuits in the processing of information in the brain.
Vesce
S
S
Institute of Pharmacological Sciences, University of Milan, Italy.
Bezzi
P
P
Volterra
A
A
D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects; D002450:Cell Communication / Q000187:drug effects; D005089:Exocytosis / Q000187:drug effects; D018698:Glutamic Acid / Q000378:metabolism / Q000494:pharmacology; D021962:Membrane Microdomains; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D013569:Synapses / Q000187:drug effects / Q000378:metabolism; D009435:Synaptic Transmission / Q000187:drug effects
D018698:Glutamic Acid; D002118:Calcium