Baroreceptor reflex control of heart rate in angiotensin type 1A receptor knockout mice

Yan-Ting Choong,Andrew M Allen,Clement Menuet,Nikola Jancovski

doi:10.1002/phy2.171

Abstract

The baroreceptor reflex dampens the short-term fluctuations in blood pressure by feedback modulation of heart rate (HR) and vascular resistance. Impairment of this reflex has been observed in hypertension and heart failure. Angiotensin II, a blood borne hormone, acts via its type 1A receptor to attenuate the baroreceptor reflex and this reflex is reported to be dramatically altered in angiotensin type 1A receptor knockout mice. This study sought to further investigate changes in the arterial and cardiopulmonary baroreceptor reflex control of HR in angiotensin II type 1A receptor knocked out mice. In artificially ventilated, isoflurane anesthetized mice, the arterial and cardiopulmonary baroreceptor reflexes were activated via injection or slow infusions, respectively, of phenylephrine and sodium nitroprusside through the jugular vein. We observed no impairment of either the arterial or cardiopulmonary baroreceptor reflex control of HR in angiotensin type 1A receptor knockout mice.

Highlights

Arterial and cardiopulmonary baroreceptors are stretchsensitive sensory afferent neurons that monitor blood vessel stretch in select vascular beds
Baseline levels of blood pressure (BP) and heart rate (HR) prior to any experimental procedures are shown on Table 1
A genotype effect (P < 0.05) on basal HR was observed with a reduction in HR in 7-month acts via the type 1A receptor (AT1AR)-KO compared to their WT counterparts (465 Æ 68 bpm vs. 551 Æ 53 bpm)

Summary

Introduction

Arterial and cardiopulmonary baroreceptors are stretchsensitive sensory afferent neurons that monitor blood vessel stretch in select vascular beds. In response to altered vascular stretch, these afferents induce a negative reflex loop that modulates autonomic and neuroendocrine function to ensure constant perfusion, of the brain, and to dampen fluctuations in arterial blood pressure (BP). A key component of this reflex is the baroreceptor-heart rate (HR) reflex which induces rapid HR responses to alterations in BP. There are three major sites of peripheral baroreceptor afferent terminals which because of their location, convey different sensory information related to the cardiovascular system. The arterial baroreceptors located in the carotid sinus and aortic arch monitor systemic and brain-directed arterial perfusion. The cardiopulmonary baroreceptors located within heart and large systemic veins detect venous pressure to primarily provide information about blood volume. Slow rises in BP tend to activate the arterial baroreceptors whereas rapid rises activate both arterial and cardiac baroreceptor pathways (Faris et al 1980)

Methods

Results

Conclusion