Neuronal activity triggers calcium waves in hippocampal astrocyte networks.
The recent discovery that the neurotransmitter glutamate can trigger actively propagating Ca2+ waves in the cytoplasm of cultured astrocytes suggests the possibility that synaptically released glutamate may trigger similar Ca2+ waves in brain astrocytes in situ. To explore this possibility, we used confocal microscopy and the Ca2+ indicator fluo-3 to study organotypically cultured slices of rat hippocampus, where astrocytic and neuronal networks are intermingled in their normal tissue relationships. We find that astrocytic Ca2+ waves are present under these circumstances and that these waves can be triggered by the firing of glutamatergic neuronal afferents with latencies as short as 2 s. The Ca2+ waves closely resemble those previously observed in cultured astrocytes: they propagate both within and between astrocytes at velocities of 7-27 microns/s at 21 degrees C. The ability of tissue astrocyte networks to respond to neuronal network activity suggests that astrocytes may have a much more dynamic and active role in brain function than has been generally recognized.
Dani
J W
JW
Department of Molecular and Cellular Physiology, Beckman Center, Stanford University School of Medicine, California 94305-5426.
Chernjavsky
A
A
Smith
S J
SJ
D000818:Animals; D001253:Astrocytes / Q000502:physiology*; D002118:Calcium / Q000502:physiology*; D046508:Culture Techniques; D003593:Cytoplasm / Q000502:physiology; D004558:Electric Stimulation; D005110:Extracellular Space / Q000502:physiology; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D006624:Hippocampus / Q000502:physiology*; D008856:Microscopy, Fluorescence; D016202:N-Methylaspartate / Q000494:pharmacology; D009434:Neural Pathways / Q000502:physiology; D009474:Neurons / Q000502:physiology*; D018377:Neurotransmitter Agents / Q000502:physiology; D051381:Rats
D005904:Glial Fibrillary Acidic Protein; D018377:Neurotransmitter Agents; D016202:N-Methylaspartate; D002118:Calcium