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Sympathetic-Adrenergic and Baroreflex Function with Aging
APS Translational Research Group
Douglas R. Seals
D.R. Seals, F. Dinenno, M. Esler and M. Chapleau
This session will focus on the key physiological
changes that occur in sympathetic nervous system-adrenergic and baroreflex
function with aging. The symposium will:
1) Establish changes in sympathetic nervous system behavior and its arterial
consequences (e.g., changes in peripheral blood flow/vascular conductance,
adrenergic tissue responsiveness, arterial hypertrophy), and baroreflex
function with aging in humans; and 2) Using an integrative (translational)
approach, draw from both the literature in humans and experimental animals
to provide insight into the physiological mechanisms underlying these
age-associated changes. Investigators and students from physiology,
pharmacology, clinical sciences, gerontology/geriatric medicine, nutritional
sciences, and exercise science will have interest in this symposium. The
autonomic nervous system (ANS) plays a key role in preserving organismic
homeostasis. The sympathetic nervous system (SNS) and the baroreflexes are
important “tools” by which the central nervous system uses the ANS to
maintain homeostasis. For over 25 years we have known that the SNS becomes
tonically, progressively and markedly activated with aging in humans.
Despite this, scientists and clinicians have little understanding of the
tissue/organ-specific changes that occur in SNS activity with human aging,
the teleology of this SNS activation, the underlying mechanisms mediating
this activation, and the adrenergic-cardiovascular consequences of this
long-term activation. Moreover, the distinct differences between changes in
sympathetic-adrenergic function with primary (physiological) aging vs aging
in the presence of chronic cardiovascular and metabolic diseases are not
well appreciated.
Similarly, although there is evidence for impaired
baroreflex function with aging dating back to the 70’s, the experimental
evidence is confusing and controversial. Some findings support reductions
in baroreflex control of the circulation with aging, whereas other data
indicate preserved baroreflex function with advancing age. The
physiological mechanisms responsible for any changes observed in baroreflex
function with aging also are poorly understood.
The importance of understanding these changes in
sympathetic-cardiovascular and baroreflex function with aging lies in part
in the related clinical implications. Aging in humans is associated with a
dramatic increase in the prevalence of a number of cardiovascular diseases.
Indeed, cardiovascular diseases are responsible for ~50% of all deaths in
the U.S. and industrialized nations. Sympathetic nervous system activation,
impaired cardiac and peripheral adrenergic function, and reduced baroreflex
circulatory control are fundamental features of a number of cardiovascular
disorders including coronary artery disease, congestive heart failure,
essential hypertension, and type 2 diabetes (an newly recognized and serious
cardiovascular disease). As such, these ANS changes may play an important
mechanistic role in the etiology of age-associated cardiovascular disease
and the resulting morbidity and mortality. The proposed symposium will
comprehensively address these important issues concerning changes
sympathetic-adrenergic and baroreflex control with physiological and
pathophysiological aging.
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