Does amlodipine affect circadian rhythms in blood pressure, heart rate, and motor activity in male Wistar rats?
Amlodipine exhibits a circadian phase-dependency in its cardiovascular effects in rats, with greater blood pressure reduction during the dark span.
In male Wistar rats light (L): 07:00–19:00 h, dark (D): 19:00–07:00 h, the effects of the calcium channel blocker amlodipine (1, 3, 10 mg/kg i.p.) on blood pressure, heart rate, and motor activity were studied by telemetric monitoring. Amlodipine was injected either at 07:00 h or at 19:00 h. Systolic and diastolic blood pressure were dose-dependently decreased with more pronounced effects in the dark span, ED50 values in D were about seven times lower than in L. In contrast, the dose-dependent increase in heart rate was more pronounced in L than in D. No significant effects of amlodipine were found on motor activity. The study gives evidence for a circadian phase-dependency in the cardiovascular effects amlodipine in rats.
Mattes et al. (Tue,) studied this question.