Influence of age on cardiovascular reflex response in anesthetized rats

Document Type

Journal Article

Publication Date

12-1-1985

Journal

American Journal of Physiology - Regulatory Integrative and Comparative Physiology

Volume

18

Issue

1

Abstract

To test the hypothesis that aging is associated with an altered hemodynamic response to physiological (nonpharmacological) stimuli, such as postural change and intravascular volume perturbations, we studied the adult (A, 6 mo) and senescent (S, 24 mo) Fischer 344 rat, a mammalian aging model not influenced by atherosclerosis or hypertension. Special emphasis was placed on the afferent limb of the baroreceptor reflex arc, an area not previously studied with respect to age. The base-line heart rate (HR), systemic arterial pressure (SAP), pulmonary arterial pressure (PAP), and carotid sinus nerve activity were not influenced by age. Following postural change (60° upward tilt), the old animals demonstrated a greater drop in systolic pressure (-11 ± 2, A; -21 ± 4 mmHg, S; P < 0.05), but there was no significant change in HR in either group. In response to a controlled withdrawal of 0.5 ml, the A had a greater reduction in systolic pressure (-29 ± 4, A; -12 ± 3 mmHg, S; P < 0.01), whereas HR or PAP did not change; both groups showed a similar decrease in nerve activity. After infusions of 0.5 and 1.0 ml, the systolic and diastolic pressure changes were greater (P < 0.02), and the changes in nerve activity appeared to be slightly more prolonged in the A compared with the S. Thus the response to changes in intravascular volume and posture are altered with age, and differences in volume-mediated venovasomotor reflex response may contribute to these age-related changes in the rat.

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