Fig. 5

Dark-light phase fluctuation in rat choroid plexus transporter function. A Schematic illustrating uptake of ⁸⁶Rb⁺ via the Na⁺/K⁺-ATPase (left panel), inhibited by ouabain (2 mM, right panel). B ⁸⁶Rb⁺ uptake in choroid plexus excised during the light (ZT 8 h) and dark phase (ZT 20 h) in the absence and presence of ouabain (marked with a red bar), n = 5–6. C The Na⁺/K⁺-ATPase-mediated ⁸⁶Rb⁺ influx was obtained from the difference between control and ouabain-treated choroid plexus within the same rat, n = 5–6. D Schematic illustrating efflux of ⁸⁶Rb⁺ via NKCC1 (left panel) and inhibited by bumetanide (20 µM, right panel). E ⁸⁶Rb⁺ efflux from choroid plexus excised during the light (ZT 8 h) and dark phase (ZT 20 h) in the absence and presence of bumetanide (marked with a red bar), n = 5–6, one outlier removed from the light phase control group. The Y-axis represents the natural logarithm of the ⁸⁶Rb⁺ amount left in the choroid plexus at time T (A_T) divided by the initial amount at time 0 (A₀). F Efflux rate constants calculated for the data displayed in E. G The NKCC1-mediated ⁸⁶Rb⁺ efflux was obtained from the difference between control and bumetanide-treated choroid plexus within the same rat, n = 5. NKA the Na⁺/K⁺-ATPase, NKCC1  the Na⁺, K⁺, 2Cl^- cotransporter. Data are shown as mean ± SD and statistical significance was evaluated with one-way ANOVA followed by Tukey’s multiple comparison test (B and F) or unpaired t-test (C and G). ***P < 0.001, *P < 0.05, ns; not significant