Figure 2.

All panels, left tracings: Construction of a cumulative concentration-effect curve for BK-induced contraction by using a ring of human umbilical vein pre-equilibrated for 3 h. Abscissa scale: time; ordinate scale: isometric contraction, grams. Δ indicates the application of BK (cumulative nanomolar concentration indicated) and ▼ the first of a series of washouts. All panels, middle tracings: the tested small molecule antagonists or their DMSO vehicle exerted no contractile effects. All panels, right tracings are recorded in the same tissues at time 5 h. The DMSO vehicle has no major effect on the previously recorded response to BK (sensitivity, maximal effect) (A). Compound 2 (B) or Compound 3 (C) at a high concentration depressed both the sensitivity of the same ring to BK and, slightly, the maximal effect of the peptide (estimated from the previously recorded E_max).