Problems, possibilities, and pitfalls in studying the arterial baroreflexes’ influence over long-term control of blood pressure

Abstract

While there is no disputing the critical role of baroreflexes in buffering rapid changes in arterial pressure, their role in long-term pressure control has become an area of controversy. Recent experiments using novel techniques have challenged the traditional view that arterial baroreflexes are not involved in setting chronic arterial pressure levels. Resetting of the arterial baroreflex, often used as an argument against the arterial baroreflex playing a role in long-term pressure control is rarely complete. The arterial baroreflex is just one of the many neural, hormonal, and intrinsic mechanisms involved in arterial pressure control and while the removal of the arterial baroreflex alone has little effect on mean arterial pressure it is too simplistic to suggest that the baroreflex has no role in long-term pressure control. Renal sympathetic nerve activity appears to be particularly resistant to resetting in response to ANG II-induced hypertension. Given the important role of the kidneys in long-term pressure control, we suggest there is a clear need to develop experimental techniques whereby sympathetic nerve activity to the kidneys and other organs can be monitored over periods of weeks to months.

Glucocorticoids act in the dorsal hindbrain to modulate baroreflex control of heart rate

“…Therefore, the effect of DHB glucocorticoids to alter baroreflex gain could contribute to their pathophysiological effects on the cardiovascular system. The effects of DHB Cort to increase the baroreflex midpoint and reduce the reflex gain could also contribute to the development or maintenance of hypertension, although the role of the baroreflex in longterm regulation of arterial pressure is controversial (3,29,32,50). In summary, the results of the present study improve our understanding of the mechanisms that account for the increased cardiovascular disease risk imposed by elevated glucocorticoids and emphasize the importance of understanding the nature and mechanisms of glucocorticoid effects on central control of autonomic function.…”

“…The arterial baroreceptor reflex is an autonomic reflex that is important for the shortterm, and possibly long-term, regulation of arterial pressure (3,29,32,50). Studies from our laboratory have demonstrated that systemic administration of corticosterone (Cort) modulates baroreflex control of both renal sympathetic nerve activity and heart rate to increase the arterial pressure midpoint and decreases the reflex gain independent of changes in arterial pressure in rats (37, 40).…”

Cardiovascular Stress Hyperreactivity in Babies of Smokers and in Babies Born Preterm

“…16 The second tests short latency, including baroreflex mechanisms that resist (buffer) sudden rises or falls in blood pressure. 17,18 Analyzing the pattern of responses to each challenge reveals how vascular and cardiac mechanisms contribute to hemodynamic stability. We looked for unusual stress reactivity patterns as evidence of early underlying, "silent" cardiovascular dysfunction consistent with the known epidemiological risks associated with being born small, early, or to a smoker.…”

To Dip or Not to Dip

“…38 Thus, the low morning angiotensin II levels might serve as one explanation for the shift of the baroreflex curve in the present study. 32,40 This hypothesis, however, cannot be established with the present study, and it is well possible that the decrease in renin and angiotensin levels just reflects the passive consequence of nondipping but has no regulatory influence on baroreflex function.…”

“…31,32 It seems that the nocturnal sleep period uniquely allows the determination of this centrally driven set point, because wakefulness inevitably blurs or continuously modifies arterial baroreflex function. Recent animal studies highlighted the possibility of such a central nervous set point, 31 and our study suggests that such superordinated central nervous control of baroreflex function exists in humans as well.…”