Fig. 4.
Substance P (SP)-induced tonic contraction in isolated rat mesenteric collecting lymphatic vessels is largely inhibited in the presence of caffeine. Representative trace of diameter over time of an isolated rat collecting lymphatic vessel before and after addition of 10−2 M caffeine, later followed by the addition of 10−8 M SP (A). *Artifact in the diameter tracking that occurred when caffeine was added. The boxes beneath the trace represent the time periods during which the quantitative data used for comparisons in B–D were collected. The mean diameter (B), mean tone (C), and maximum tone (D) for the time periods before addition of SP, 0–30 s after SP addition, and 31–150 s after addition of SP were compared using a repeated measures ANOVA model followed by Dunnett’s comparison with control (Before SP). N = 7 isolated lymphatics were studied. Each lymphatic studied was obtained from a unique rat. NS, not significant.