Synaptic vesicle release does not regulate overall exploratory behavior of all oligodendrocyte process extensions. (A) Representative confocal time-lapse images of TdTomato-CaaX labeled single oligodendrocytes (anterior left, dorsal side up). Within time-lapse series insets, E, R and S denote process extensions, retractions and stalls, respectively. (B) Pie charts display the proportion of processes that extended, retracted, or stalled during time-lapse imaging. Statistical testing (ordinary one-way ANOVA, Dunnett’s post-test) indicated increased stall behavior in the Latrunculin A (125 nM) group (p < 0.0001 for LatA vs. control) but no change caused by TeNT-LC (p = 0.87 for TeNT-LC vs. control). (C) Graph depicts the frame-to-frame rate of process movements, with individual points representing the average distance that individual processes moved during each 15 s time-lapse interval (per cell). Sample size (tracked processes, cells, animals) = 39, 8, 8 (control), 60, 8, 7 (TeNT-LC), 106, 19, 19 (Latrunculin A). (D) Composite images represent the extent of process movements during a 15 min time-lapse imaging window. Blue shaded areas represent the morphology of individual oligodendrocytes at the time of the first time-lapse frame. Magenta shaded areas represent all pixels surrounding the original position where processes moved into or occupied for one or more frames during the time-lapse. This magenta shaded region is a maximum intensity over time projection, thereby representing the history of process movements surrounding the blue first frame position. Scale bar = 5 μm. (E) Summary of the percentage of the area (μm2) surrounding the blue first frame position that was occupied by processes during the time-lapse (magenta). Percentage of area measurements were restricted to a 1.5 μm band surrounding the blue first frame position. Each data point represents the average percentage of area within the 1.5 μm band occupied by processes of individual oligodendrocytes (per cell). Sample size (individual cells, animals) = 10, 10 (control), 12, 11 (TeNT-LC), 15, 15 (Latrunculin A). For (C) and (E), bars represent mean ± SEM; Ordinary one-way ANOVA, Dunnett’s post test.
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