Cholinergic activity induces astrocyte Ca²⁺ elevations and LTP in CA3-CA1 synapses in the hippocampus in vivo.

<p>(A) Schematic drawing of the experimental approach used to monitor Ca²⁺ levels in hippocampal astrocytes in vivo; representative images of astrocytes labeled with sulforhodamine 101 (SR101) and loaded with Fluo-4-AM; corresponding merge image; and image of Fluo-4-loaded astrocytes displaying regions of interests. Scale bar, 20 µm. (B) Fluorescence traces of Ca²⁺ levels in regions of interests in astrocytes showed in (A) evoked by tail pinch sensory stimulation (horizontal bars) in control and in the presence of atropine. (C) Proportion of astrocytes responding to sensory stimulation in control (66 astrocytes from <i>n</i> = 8 rats), atropine (32 astrocytes from <i>n</i> = 4 rats), and MCPG (15 astrocytes from <i>n</i> = 3 rats). (D) Schematic drawing of the in vivo experimental approach showing the stimulating electrode in the Schaffer collaterals (SC) and the extracellular recording electrode of fEPSPs placed in the hippocampal CA1 region, and a representative trace of a field potential showing hippocampal theta rhythm activity (bottom) during tail pinch sensory stimulation. Right, Relative fEPSP slope (from basal values) versus time. Zero time corresponds to the onset of stimulation (as in all other figures). Inset: mean fEPSPs before and 60 min after stimulation. (E) Average relative changes of fEPSP evoked 60 min after sensory stimulation in control (<i>n</i> = 7), atropine (<i>n</i> = 6), and MCPG (<i>n</i> = 6). (F) Schematic drawing showing the additional stimulating electrode in the medial septum nucleus. Right, Relative fEPSP slope (from basal values) versus time. Zero time corresponds to the onset of stimulation that lasted 90.7 s (horizontal bar). Inset: mean fEPSPs before and 60 min after septum stimulation. (G) Average relative changes of fEPSP evoked 60 min after stimulation in control (<i>n</i> = 9), atropine (<i>n</i> = 6), and MCPG (<i>n</i> = 6). ***<i>p</i><0.001. Data are presented as means ± s.e.m (as in all other figures).