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. Author manuscript; available in PMC: 2022 Sep 2.
Published in final edited form as: Nat Methods. 2019 Oct 28;16(11):1119–1122. doi: 10.1038/s41592-019-0597-2

Figure 2 ∣. Microcirculation and fast contractions of cerebral bridging veins.

Figure 2 ∣

(a) Conventional epi-fluorescence image in motor cortex of an anesthetized mouse after intravenous administration of rhodamine-B. Dashed box encloses the artery in b.

(b) Image time series (2.5 ms per frame; 200 kHz laser pulse rate; 2.2 mW per beamlet) taken by high-speed two-photon imaging reveals flow of injected, fluorescent HEK-293 cells. Arrowheads mark a cell’s progress.

(c) Flow speed map for the vessel in b.

(d) Trajectories of individual HEK-293 cells. Each trajectory is encoded in color and superposed on an epi-fluorescence image of the vasculature.

(e) Flow speeds in neocortical arteries had a parabolic cross-sectional profile. For 15 different cross-sections chosen within 3 different arteries (>50 μm in diameter; N = 3 mice), we computed flow speeds, V(r), as a function of the radial deviation, r, from the vessel’s longitudinal axis. We fit (red curve) the data (blue points) to V/Vmax = 1 – (r/R)n , where Vmax is each vessel’s peak flow speed and R is its radius. The fitting parameter, n = 2.0 ± 0.3 (95% C.I.), revealed the flow speed’s quadratic profile. Error bars: s.e.m. (N = 15 cross-sections).

(f) Flow speed map determined by 1-kHz-two-photon imaging (200 kHz laser repetition rate; 2.9 mW per beamlet; 450 × 110 μm2 field of view).

(g) Trajectories of individual HEK-293 cells, determined from the same dataset used for f.

(h) Periodic fluctuations in blood flow, as computed within the encircled area in f. The heart rate of ~150 beats·min−1 determined by high-speed imaging matches conventional measurements in ketamine-xylazine-anesthetized mice17.

(i) Sketch of the mouse superior sagittal sinus (SSS). Inset: We targeted areas near bregma for imaging (dotted rectangle).

(j) Example time traces of bridging vein diameter determined by 200-Hz-imaging (450 × 300 μm2 field of view; 200 kHz laser pulse rate; 2.2 mW per beamlet) after intravenous injection of rhodamine-B. During wakefulness, the vein diameter (blue trace) exhibited fast constriction (red dots) and dilation (cyan dots), which anesthesia abolished (gray trace).

(k) Negative- and positive-going changes in vein diameter, relative to each vessel’s mean diameter, during constriction (red curve) and dilation (blue curve) in 4 awake mice. Constriction and dilation rates were, respectively, −6.5 ± 0.9% and +4.0 ± 0.7% per 100 ms (mean ± s.e.m; 36 events of each type). Shading: s.e.m.

Scale bars: 50 μm in a–d, f, g.