Cytosolic Ca2+ signals in astrocytes can be spontaneous or evoked, and they are often initiated by activation of metabotropic receptors, resulting in Ca2+ release from intracellular Ca2+ stores. Although voltage-dependent Ca2+ influx is rare in astrocytes, the refilling of the intracellular Ca2+ stores requires store-operated Ca2+ entry, a major influx pathway of Ca2+ into astrocytes. Astrocyte Ca2+ signals are generated in the form of transients or oscillations, which can be evoked by neurotransmitters, hormones, cytokines, and growth factors, often in response to neuronal activity. These Ca2+ signals are propagated along cellular processes and can travel from the point of origin across the tissue as Ca2+ waves. When propagated into astrocytic endfeet, they may release cyclooxygenase products to control cerebral blood flow. Astrocyte Ca2+ signaling may lead to the release of transmitters and may be one of the key mechanisms for allowing a complex dialogue between neurons and glial cells.
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