Figure 1. The effect of LDT at the central site on resting feed artery diameter and vasodilatation in response to acetylcholine.

A, illustration of the experimental design. The retractor muscle (RET) is shown reflected away from the hamster with the direction of blood flow indicated along the feed artery (other vessels are omitted for clarity). Asterisks indicate sites at which diameter measurements were obtained: the distal site (D) was just external to the muscle; the central site was 500 μm upstream and centred within the segment exposed to LDT (see Methods); the proximal site (P) was 1000 μm upstream from the distal site. B, resting diameter (filled symbols) and corresponding change in diameter (open symbols; calculated as peak minus rest values) in response to the microiontophoretic application of acetylcholine (1000 nA, 500 ms) at the central site during LDT (n = 9). Each period of illumination lasted 6 min, with vessel diameter and vasodilatation evaluated after 5 min of recovery. Vasodilatation decreased progressively during LDT and was abolished following the fourth period of illumination. Maximal diameter, 98 ± 4 μm. * P < 0.001, main effect of LDT; one-way repeated measures ANOVA.