Hypotensive effects of dihydropyridine derivatives.

Effects of six dihydropyridine derivatives (nifedipine, nisoldipine, nitrendipine, nicardipine, nimodipine and niludipine) and hydralazine on blood pressure and heart rate in spontaneously hypertensive rats (SHR) were studied in comparison with those in normotensive rats (NR). Nisoldipine, nitrendipine and nicardipine showed stronger hypotensive effect in SHR than in NR. All the dihydropyridine derivatives--especially nifedipine, nitrendipine and niludipine--lowered blood pressure of SHR at doses smaller than those producing positive chronotropic effect. Hydralazine caused hypotensive effect in the same extent both in SHR and in NR and, moreover, it brought about tachycardia at doses smaller than those lowering blood pressure.