Decoding calcium wave signaling

Abstract

This chapter reviews that intercellular calcium waves in astrocytes represent a phenomenon whereby a wave of increases in free cytosolic calcium concentration ([Ca2+]i) spreads from an initially stimulated cell across an astrocytic syncytium. Three key factors merged to trigger the discovery of calcium waves in the astrocyte syncytium. The first was finding that astrocytes possessed a full array of neurotransmitter receptors that operated on a millisecond time frame similar to that expected by neurons. The second contribution was the many technological advances made in time-lapse video microscopy, particularly involving the newly marketed confocal scanning laser microscope, which allowed longer recording periods free of phototoxicity. Lastly, most critical was the development of Ca2+ sensitive fluorescent probes that were ion-specific that allowed precise quantification of changes in intracellular Ca2+. The chapter also explores that nitric oxide (NO)-mediated signaling mechanisms are involved, but only in some types of calcium waves, especially those triggered by mechanical stimulation. Neuronal activity also induces astrocytic calcium waves by stimulation of metabotropic glutamate receptors on astrocytes. In turn, glutamate release from astrocytes sustaining a calcium wave is capable of triggering neuronal activity.