Effect of K-7259, a novel derivative of dilazep, on cardiovascular actions of adenosine: comparison with dilazep.

The effect of K-7259, a novel derivative of dilazep, on the cardiovascular action of adenosine was studied in the aortic ring and isolated perfused heart in guinea-pigs, and compared with that of dilazep. Adenosine produced a concentration-dependent relaxation in phenylephrine (2 x 10(-6) M)-contracted aortic rings and exhibited a negative chronotropic effect in the isolated perfused heart. Dilazep (10(-8), 10(-7) and 10(-6) M) potentiated significantly the relaxing action of adenosine on the aortic ring in a concentration-dependent way. K-7259 (10(-6) M), however, did not potentiate the relaxing action of adenosine, although the high concentration of K-7259 (10(-5) M) potentiated it slightly but significantly. The negative chronotropic effect of adenosine was also potentiated by dilazep (10(-7) and 10(-6) M), but not by K-7259 (10(-6) M). These results suggest that the potentiating action of K-7259 on the cardiovascular effects of adenosine is very weak when compared with that of dilazep.