Fig. 4. Astrocytic Ca2+ activity in processes and soma is highly
heterogeneous. (A) Left: 3D reconstruction of a hippocampal astrocyte in
situ (core structure); processes are color-coded according to average
activity level. Right: Distribution of all processes from recordings in situ
(n = 72) based on individual mean Ca2+ activity. See also fig. S4, A and B.
(B) Effect of TTX on basal Ca2+ activity in individual processes in situ
(n = 21); color coding highlights different levels of inhibition (high, >75%;
medium, 25 to 75%; no, <25%). (C) Voxel activity map showing microscopic
heterogeneity of Ca2+ activity within each process and surroundings (P1 and
P2, processes; S, soma; EF, endfoot; g, gliapil; voxel size, 1 mm3). Note the hot
spots (yellow) and cold regions (brown) along the process. (D) Distribution
of local Ca2+ activity within each individual process versus distance from soma
(n = 17 medium- and high-activity processes). Activity was calculated voxel-
by-voxel (size, 1 mm3) and normalized to maximal activity in the process.
Asterisks denote endfoot-related processes. (E) Left: Distribution of spatial
spread versus total duration (semilogarithmic scale) of Ca2+ events involving
the astrocytic soma (ex vivo, n = 29; in vivo, n = 11; symbol and scale color
code: in vivo, teal; ex vivo, maroon). Right: Representative examples of
spatially heterogeneous somatic events overlaid on the astrocytic
morphology (red, ex vivo; green, in vivo). See also fig. S4C. (F) Temporal
cross-correlation projection map (30-mm stack) of GCaMP6f activity indicating
multifocal origination of a global event in vivo; “lead” voxels (shades of red)
precede the main event cluster at the astrocyte periphery, mainly in the gliapil.
Core structure is outlined; b.v., blood vessel. See also fig. S6.