The effects of age on baroreceptor reflex function in man

Abstract

IT IS WELL KNOWN that baroreceptor reflex activity is an important factor in the acute homeostatic regulation of the cardiovascular system, particularly under stressful conditions such as haemorrhage or sudden postural changes. 1-4 Despite the numerous changes observed in cardiovascular structure and function that occur with aging, 5-13 the relationship between aging and baroreceptor reflex function has not been clarified. Earlier work by Norris, et al. TM using tilting techniques observed reflex changes in heart rate and blood pressure in normal subjects and ambulatory patients ranging in age from 20 to 92 years. The elderly subjects showed the greatest decrease in blood pressure with the least change in heart rate, suggesting that with aging there is some alteration in the reflex regulation of the cardiovascular system.Wade, et al., utilizing the Valsalva maneuver to quantitate baroreeeptor reflex function, showed the baroreeeptor reflex activity appeared to decrease with age. 1~ However, a majority of patients studied had some clinically significant occlusive cerebral vascular disease. In three recent studies utilizing techniques of stressing the baroreceptor mechanisms by pharmacologically induced hypertension, Bristow, et al., 1~ Eckberg, et al.y and Gribbin, et al3 s found a negative correlation between baroreceptor reflex function and age. Bristow, et al. studied normotensive and hypertensive subjects. Baroreflex function was decreased in their hypertensive subjects. An inverse relationship between age and baroreflex function was apparent when all subjects were considered irrespective of their baseline blood pressures. In Eekberg's studies, a similar relationship between age and baroreceptor reflex function was observed in 23 subjects with no demonstrable cardiovascular disease. The majority of their controls (15 subjects) were between the ages of 15 and 30 years. Because only 3 subjects were over the age of 45 years, we felt that the age spectrum covered was inadequate. Gribbin, et al. observed that baroreflex sensitivity was independently reduced by increasing age and blood pressure in a larger number of subjects than the latter study. The purpose of this present study was to examine the relationship between aging and baroreflex funetion in man by utilizing two quantitative tests of baroreflex fun+ tion. The tradition/d Valsalva maneuver test as described by Sharpey-Schafer, 19 which stimulates the baroreflex by producing a transient arterial hypotension and the pressor test described by Smyth, Sleight, and Piekering, 2~ which is based on producing a baroreflex response to pharmacologically induced hypertension.

Sensitivity of rapidly acting arterial pressure control system in conscious adult rabbits at different ages.

“…Therefore, pentobarbital anesthesia does not seem to affect the G value. The results of this study differ from the general assumption found in the literature that baroreceptor sensitivity declines with aging (GRIBBIN et al, 1971;FROLKis et al, 1975;DUKE et al, 1976;VLACHAKis et al, 1976;RANDALL et al, 1978). Earlier studies, however, were based on the relationship between heart period and systolic arterial pressure changes in response to intravenous injection of pressor agents.…”

The Effects of Aging on Somatocardiac Reflexes in Anesthetized Rats

“…It is well known that, in the elderly, cardiac function is well maintained at rest, but its ability to adjust to environmental changes is reduced compared to younger individuals [1]. For example, the cardiac response to changes in blood pressure (baro-reflex) decline with advancing age [2,3] as a result of reduced sensitivity of baroreceptors [4][5][6].Cardiac responses to changes in the external environment, such as the bradycardia that results from exposure of the face to cold temperatures, also decrease with age [7], though the mechanism by which this occurs remains to be elucidated. It has been reported that nociceptive stimulation of the skin in anesthetized adult animals results in a reflexive increase in HR that Japanese Journal of Physiology, 54, 137-141, 2004 Key words: heart rate, cardiac sympathetic nerve, somatocardiac reflex, aging, ␤-adrenergic receptor.…”

“…It is well known that, in the elderly, cardiac function is well maintained at rest, but its ability to adjust to environmental changes is reduced compared to younger individuals [1]. For example, the cardiac response to changes in blood pressure (baro-reflex) decline with advancing age [2,3] as a result of reduced sensitivity of baroreceptors [4][5][6].…”

Arterial Pressure and Its Variability in Conscious Rabbits at Different Ages

“…To the contrary, it has been reported that baroreflex function decreased with aging in man [5,7,9,20] . In most these investigations, the effects of aging on baroreflex function were estimated from relationship between heart rate and systemic AP changes in response to vasoactive drugs, which does not mean baroreflex control of AP.…”

“…Effects of aging on arterial pressure (AP) control system have often been assessed from responses of AP to vasoactive drugs [5,7,9,19,20] or to exercises [2,14,18,211. Most of these studies showed physiological alteration of the AP control system with aging when the responses were recorded even in a short period of time under unanesthetized conditions.…”