RT Journal Article SR Electronic T1 Stimulation-Evoked Ca2+ Signals in Astrocytic Processes at Hippocampal CA3–CA1 Synapses of Adult Mice Are Modulated by Glutamate and ATP JF The Journal of Neuroscience JO J. Neurosci. FD Society for Neuroscience SP 3016 OP 3021 DO 10.1523/JNEUROSCI.3319-14.2015 VO 35 IS 7 A1 Tang, Wannan A1 Szokol, Karolina A1 Jensen, Vidar A1 Enger, Rune A1 Trivedi, Chintan A. A1 Hvalby, Øivind A1 Helm, P. Johannes A1 Looger, Loren L. A1 Sprengel, Rolf A1 Nagelhus, Erlend A. YR 2015 UL http://www.jneurosci.org/content/35/7/3016.abstract AB To date, it has been difficult to reveal physiological Ca2+ events occurring within the fine astrocytic processes of mature animals. The objective of the study was to explore whether neuronal activity evokes astrocytic Ca2+ signals at glutamatergic synapses of adult mice. We stimulated the Schaffer collateral/commissural fibers in acute hippocampal slices from adult mice transduced with the genetically encoded Ca2+ indicator GCaMP5E driven by the glial fibrillary acidic protein promoter. Two-photon imaging revealed global stimulation-evoked astrocytic Ca2+ signals with distinct latencies, rise rates, and amplitudes in fine processes and somata. Specifically, the Ca2+ signals in the processes were faster and of higher amplitude than those in the somata. A combination of P2 purinergic and group I/II metabotropic glutamate receptor (mGluR) antagonists reduced the amplitude of the Ca2+ transients by 30–40% in both astrocytic compartments. Blockage of the mGluRs alone only modestly reduced the magnitude of the stimulation-evoked Ca2+ signals in processes and failed to affect the somatic Ca2+ response. Local application of group I or I/II mGluR agonists or adenosine triphosphate (ATP) elicited global astrocytic Ca2+ signals that mimicked the stimulation-evoked astrocytic Ca2+ responses. We conclude that stimulation-evoked Ca2+ signals in astrocytic processes at CA3–CA1 synapses of adult mice (1) differ from those in astrocytic somata and (2) are modulated by glutamate and ATP.