Figure 1.

An experimental trace (A) and the results from several experiments (B) showing that in the absence of tone, flow for 5 min at 5 mL·min⁻¹ elicited only a barely detectable constrictor response in rat carotid artery segments. The sequential addition of L-NAME (100 µM), indomethacin (Indo, 3 µM), then apamin (Ap, 0.5 µM) and TRAM-34 (10 µM), to block any opposing dilator effects of NO, prostanoids or EDHF, had no effect on the magnitude of this constriction. However, following induction of low-level tone using U46619, flow elicited a small transient dilatation followed by a more powerful constriction that was sustained until the termination of flow. The 5 min periods of flow are indicated by the time bars. The pressure trace (in mmHg) shows that flow was induced while maintaining constant pressure. Data are presented as the mean ± SEM of five observations. ***P < 0.001 indicates a significant difference from control.