A-C, Arterial dilation following 40 s constriction evoked by KCl (40 mM) or blue light (TRPV1-ChR2 mice) and the reemergence of tone. BCTC and disruption of the TRPV1 gene inhibits the magnitude of the dilation and rate of recovery of tone (WT, n = 5 mice, 5 arteries; WT+BCTC, n = 5 mice, 5 arteries; TRPV1-null, n = 4 mice, 4 arteries; TRPV1-ChR2, n = 5 mice, 5 arteries, unpaired t-test). D-F, Dilation of medium- (~60 μm) and small (~25 μm) diameter arteries in response to 4 s blue light (TRPV1-ChR2 mice) or 6 s application of 40 mM KCl (WT, 60 μm, 3 mice, 3 arteries; 25 μm, 5 mice, 5 arteries; TRPV1-null, 60 and 25 μm, n = 4 mice, 4 arteries; TRPV1-ChR2, n = 5 mice, 5 arteries, unpaired t-test).