Sustained diurnal blood pressure reduction in SHR with ramipril assessed by telemetric monitoring.

Subchronic bolus administration of the angiotensin-converting-enzyme inhibitor ramipril caused a dose-dependent (0.1 to 10 mg.kg(-1).d(-1)), yet each in his own way 24-hour sustained, reduction in arterial blood pressure in conscious unrestrained spontaneously hypertensive rats with telemetric recording, and 0.01 mg.kg(-1).d(-1) was a no-effect dose. This was accompanied by dose-dependent attenuation of heart rate lowering during periods of low locomotor activity. Neither effect persisted for more than a few days after cessation of the medication with full restoration of pretreatment levels. No dosage altered the circadian rhythm of blood pressure, heart rate and locomotor activity of the rats.