Fig. 3.

Substance P (SP) elicits constriction of isolated rat mesenteric collecting lymphatic vessels during blockade of L-type Ca²⁺ channels with nifedipine. Representative trace of diameter over time of an isolated rat collecting lymphatic vessel before and after addition of 10⁻⁷ M nifedipine, later followed by the addition of 10⁻⁸ M SP (A). 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 (baseline period). P values for the comparisons are shown. N = 6 isolated lymphatics. Each lymphatic studied was obtained from a unique rat. NS, not significant.