Abstract
Abnormal blood pressure (BP) elevation in early morning is known to cause cardiovascular events. Previous studies have suggested that one of the reasons in abnormal dairy BP variability is sympathoexcitation. We have demonstrated that brain angiotensin II type 1 receptor (AT1R) causes sympathoexcitation. The aim of the present study was to investigate whether central AT1R blockade attenuates the excess BP elevation in rest-to-active phase in hypertensive rats or not. Stroke-prone spontaneously hypertensive rats (SHRSP) were treated with intracerebroventricular infusion (ICV) of AT1R receptor blocker (ARB), oral administration of hydralazine (HYD), or ICV of vehicle (VEH). Telemetric averaged mean BP (MBP) was measured at early morning (EM), after morning (AM), and night (NT). At EM, MBP was significantly lower in ARB to a greater extent than in HYD compared to VEH, though MBP at AM was the same in ARB and HYD. At NT, MBP was also significantly lower in ARB than in HYD. These results in MBP were compatible to those in sympathoexcitation and suggest that central AT1R blockade attenuates excess BP elevation in early active phase and continuous BP elevation during rest phase independent of depressor response in hypertensive rats.
Highlights
Hypertension is established as a major risk factor for cardiovascular disease, and antihypertensive treatments are necessary to prevent the cardiovascular events [1]
At early morning (EM), mean BP (MBP) was significantly lower in AT1R receptor blocker (ARB) to a greater extent than in HYD compared to VEH, though MBP at after morning (AM) was the same in ARB and HYD (Figure 1)
Throughout EM, AM, and NT, LFnuSBP was significantly lower in ARB than in HYD and VEH
Summary
Hypertension is established as a major risk factor for cardiovascular disease, and antihypertensive treatments are necessary to prevent the cardiovascular events [1]. We have already various and effective antihypertensive agents. Among the unmet prevention for hypertensive cardiovascular events, early morning blood pressure elevation is known to be associated with cardiovascular events [4, 5]. Recent several studies have suggested that morning surge should be a crucial target of the treatments for hypertension [6,7,8]. There are so much various factors to cause morning surge [4, 5], and, among the factors, sympathoexcitation and baroreflex dysfunction are closely associated with blood pressure elevation in the early morning [9]
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