Figure 4

Ranolazine antagonizes the α-adrenergic response.
(A) The effect of ranolazine was evaluated on the contraction induced by a submaximal concentration of Phe. The left panel illustrates typical relaxation induced by cumulative concentrations of ranolazine (0.1 to 200 μM) when the aorta was previously contracted with Phe (1 μM). Right panel shows dose-response curve for ranolazine. Data represent the percentage of contraction relative to the maximal tension induced by Phe (n = 10 aortas, each protocol performed in duplicate). (B) The contractile response to Phe was evaluated in the absence or in the presence of ranolazine. Left panels illustrate variations in isometric tension induced by cumulative concentrations of Phe under basal conditions (top) and after a 15-min incubation with ranolazine (20 μM; bottom). Graph shows dose-response curves for Phe under each condition (n = 10 aortas, protocol performed in duplicate). The inset shows the maximal contraction (in g) induced by Phe. (C) Effect of ranolazine on the Phe-induced (Ca+2)i increase on cultured SMCs. (Upper panel) Representative recordings of the fluorescence ratio illustrate the increase induced by Phe (1 μM) in the absence or in the presence of ranolazine (20 μM) on cultured SMCs. Arrows indicate the time of application of Phe. (Lower panel) Bar graph representing the (Ca+2)i increase induced by Phe for basal condition (Ctl) and in the presence of prazosin (10 μM), ranolazine (20 μM), TTX (1 μM) or TTX plus ranolazine. Data are expressed as percent of the response induced by the first application of Phe on the same cellular field and represent the mean ± sem of 5 different cell cultures (average of 4 cover glasses/fields for each experimental condition per cell culture). (D) Effect of ranolazine on the binding of fluorescent prazosin (QABP) in the rat aorta. The control (Ctl) shows the intensity of fluorescence obtained with QABP alone. Non-fluorescent antagonists (prazosin, Phe and ranolazine) were used to compete with QABP for binding, resulting in reduced fluorescence. **p < 0.01; ***p < 0.001, two-way Anova followed by Bonferroni post-test for vascular reactivity and Kruskal-Wallis one-way analysis of variance followed by Dunn’s test for Ca2+ imaging.