Carotid sinus baroreceptor reflex control of the circulation in medial sclerotic and renal hypertensive rabbits and its modification by the aortic baroreceptors.

Abstract

SUMMARY We studied the reflex control of blood pressure, heart rate, and hindlimb vascular resistance by the carotid sinus baroreceptors in normal (N), experimental renal hypertensive (RH, one kidney renal wrap model), and medial sclerotic (MS) rabbits under urethane anaesthesia using an isolated perfused carotid sinus preparation and auto-perfused hindlimb. The contralateral carotid sinus was denervated. Compared to N rabbits, the blood pressure and hindlimb vascular resistance of RH and MS rabbits were significantly elevated at all carotid sinus pressures 15 weeks after inducing the disease process. The maximum gains of the curves relating carotid sinus pressure to vascular resistance were significantly elevated in the MS and RH rabbits, but those relating carotid sinus pressure to heart rate were significantly reduced. The changes were greatest in the RH group in which the responses also were set to a higher carotid sinus pressure. In the three groups, division of the aortic nerves produced different changes in the sigmoid curves relating carotid sinus pressure to heart rate, blood pressure, and vascular resistance. There was a linear relationship between blood pressure and basal vascular resistance (correlation coefficient 0.88). Circ Res 47: 890-901, 1980

Arterial baroreflexes in renal hypertensive rabbits. Selectivity and redundancy of baroreceptor influence on heart rate, vascular resistance, and lumbar sympathetic nerve activity.

“…This finding has been taken to indicate a generalized impairment of the arterial baroreflexes, including baroreflex control of the peripheral circulation. Our data, as well as the work of others (Angell-James and George, 1980;Guo and Thames, 1983;Mancia et al, 1979), indicate that the impairment of baroreflex control of heart rate cannot be taken as evidence for a generalized impairment of arterial baroreflexes. It is equally important to emphasize that preservation of baroreflex control of hindlimb resistance and LSNA should not be extrapolated to other vascular beds.…”

Baroreflex Control of Sympathetic Nerve Activity in Essential and Secondary Hypertension

“…This is because although some studies have reported vascular, blood pressure, and sympathetic responses to baroreceptor manipulation to be reduced in hypertensive animals and humans, [4][5][6] other studies have found vascular, blood pressure, and sympathetic effects of alterations in baroreceptor activity to be unmodified or enhanced in experimental or human hypertension as compared with the normotensive condition. [7][8][9][10][11] This has led to the hypothesis that baroreceptor control of the cardiovascular functions is desmogenously affected by high blood pressure, ie, that this condition impairs baroreceptor modulation of sinus node but not of sympathetic nerve activity and peripheral circulation. In the present study, we tested this hypothesis in normotensive subjects, moderate or more severe essential hypertensive subjects, and secondary hypertensive subjects in whom reflex heart rate responses to baroreceptor stimulation and deactivation by vasoactive drugs were measured together with reflex changes in sympathetic nerve traffic, as quantified by microneurography.…”

Enhanced responsiveness to carotid baroreceptor unloading in conscious dogs during development of perinephritic hypertension.

“…28 -29 The state of the peripheral resistance component of the baroreceptor reflex in hypertension is a more controversial issue. Gordon and Mark 30 found impaired baroreflex control of hind limb vascular resistance in prehypertensive rats, while Angell-James and George 8 and Guo et al 12 found hind limb vascular resistance and lumbar sympathetic nerve activity, respectively, to be preserved during baroreceptor stimulation in renal hypertensive rabbits. It is important to recognize that the responses of one bed may not reflect the responses of the total systemic vasculature.…”

“…10 However, regulation of baroreceptor control of arterial pressure and vascular resistance during development of hypertension remains controversial. For example, Mancia et al" reported normal baroreflex control of blood pressure in humans with hypertension, and Angell-James and George 8 and Guo et al' 2 demonstrated baroreflex control of hind limb vascular resistance and sympathetic nerve activity were preserved in the early stages of hypertension despite impairment of baroreflex control of heart rate. However, relatively few studies have been conducted in which baroreceptor control of cardiac output has been measured, despite the importance of this variable in determining arterial pressure.…”

“…In addition, at the same weekly intervals, bolus injections of phenylephrine (10 Mg/kg i.v.) were administered in 6 of the 14 dogs, and the pulse interval/systolic arterial pressure (PI/SAP) slopes were determined according to the Smyth et al' 8 method. Finally, to compare the effects of a different hypotensive stimulus, bolus injections of nitroglycerin (10 /ig/kg i.v.)…”