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Very low frequency blood pressure variability is modulated by myogenic vascular function and is reduced in stroke-prone rats.

Abstract：

BACKGROUND:Cerebrovascular myogenic function, which protects the brain from hemorrhagic stroke, is impaired in stroke-prone spontaneously hypertensive rats. Furthermore, myogenic function contributes to very low frequency blood pressure variability and dynamic autoregulation of cerebral blood flow is most effective at very low frequency in rats. Therefore, we hypothesized that very low frequency blood pressure variability is reduced in stroke-prone spontaneously hypertensive rats compared with stroke-resistant spontaneously hypertensive rats. In addition, we investigated if myogenic function also contributes to very low frequency blood pressure variability in conscious dogs. METHODS:In 8-week-old normotensive Wistar-Kyoto rats, 8-week-old and 15-week-old stroke-prone spontaneously hypertensive rats and stroke-resistant spontaneously hypertensive rats, and dogs, blood pressure variability was studied during control conditions, inhibition of myogenic function (nifedipine) and hypotension induced by sodium nitroprusside. In dogs, transfer function analysis between blood pressure and total peripheral resistance was performed to study the contribution of myogenic function to blood pressure variability. RESULTS:Inhibition of myogenic function, but not hypotension induced by sodium nitroprusside, significantly reduced very low frequency variability of systolic blood pressure (rats: 0.02-0.2 Hz; dogs: 0.02-0.075 Hz) in conscious rats and dogs. In dogs, the gain of the transfer function was high (0.28 +/- 0.04 min/l) in the very low frequency band and was decreased to 0.11 +/- 0.01 min/l (P < 0.05) by nifedipine but not by sodium nitroprusside (0.26 +/- 0.02 min/l). Very low frequency blood pressure variability was significantly smaller in stroke-prone spontaneously hypertensive rats than in stroke-resistant spontaneously hypertensive rats (8 weeks of age: 7.8 +/- 1.1 vs. 13.1 +/- 2.2 mmHg; P < 0.05; 15 weeks of age: 7.1 +/- 1.2 vs. 16.5 +/- 3.6 mmHg; P < 0.05). CONCLUSION:Myogenic function affects very low frequency blood pressure variability in conscious rats and dogs. The smaller very low frequency blood pressure variability in stroke-prone spontaneously hypertensive rats compared with stroke-resistant spontaneously hypertensive rats suggests that impaired cerebrovascular myogenic function is reflected in reduced very low frequency blood pressure variability.

journal_name

J Hypertens

journal_title

Journal of hypertension

authors

Stauss HM,Petitto CE,Rotella DL,Wong BJ,Sheriff DD

doi

10.1097/HJH.0b013e3282fb81c8

subject

Has Abstract

pub_date

2008-06-01 00:00:00

pages

1127-37

issue

eissn

0263-6352

issn

1473-5598

pii

00004872-200806000-00012

journal_volume

pub_type

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Very low frequency blood pressure variability is modulated by myogenic vascular function and is reduced in stroke-prone rats.