Supplementary Figure 11: Capillary hyperemia to 10 mM K⁺ persisted in the presence of tetrodotoxin (TTX), a blocker of voltage-dependent Na⁺ channels.

(A) Contralateral whisker stimulation increased capillary flux under basal conditions, and this response was eliminated by application of 3 μM TTX to the cranial surface (n = 5 paired experiments, 5 mice; **P = 0.0039, two-way ANOVA with post hoc Tukey's multiple comparisons test). (B) In the presence of TTX, application of 10 mM K⁺ to the capillary still caused an increase in RBC flux and velocity, as evidenced by the increased number and steeper angle of RBCs (black streaks against the green FITC-loaded plasma) passing through the line-scanned region. Left: baseline distance-time line scan plot; right: after application of 10 mM K⁺. (C) Typical RBC flux-time plot indicating marked hyperemia after in vivo application of 10 mM K⁺ to a capillary, after pre-treatment with 3 μM TTX to silence neuronal activity. (D) Summary data for the peak increase in capillary RBC flux evoked by 10 mM K⁺ in the presence of TTX (n = 5 paired experiments, 5 mice; *P = 0.0354 (t₄ = 3.123) paired Student's t-test). Error bars represent s.e.m.