Comparative antihypertensive effects of nifedipine and nicardipine in adult and aged spontaneously hypertensive rats.

Effects of two dihydropyridine derivatives, nifedipine and nicardipine, on systolic blood pressure and heart rate in adult (4- to 5-month-old) spontaneously hypertensive rats (SHR) were studied in comparison with those in aged (11- to 12-month-old) SHR. Both calcium channel blockers induced similar dose-dependent hypotensive effects in 4- to 5-month- and 11- to 12-month-old SHR. The maximal hypotensive action of both calcium channel blockers was delayed in aged SHR compared to adult SHR. Nicardipine induced a similar reflex tachycardia in adult and aged SHR. In contrast to nicardipine there was no increase in heart rate after administration of nifedipine in aged SHR at same hypotensive effects. It is concluded that nifedipine and nicardipine are potent antihypertensive agents in aged SHR which differently affect heart rate.