Journal of Applied Physiology, Vol 80, Issue 3 869-875, Copyright © 1996 by American Physiological Society

ARTICLES

Delayed and diminished pressor response to muscle sympathetic nerve activity in the elderly

Y. Sugiyama, T. Matsukawa, A. S. Shamsuzzaman, H. Okada, T. Watanabe and T. Mano
Department of Autonomic and Behavioral Neurosciences, Research Institute of Environmental Medicine, Nagoya University, Japan.

We studied the effects of aging on alpha-receptor-mediated vasoconstrictive responses to sympathetic nerve activity in 16 healthy aged [75.8 +/- 2.7 (SE) yr] and young men (33.8 +/- 2.0 yr). Muscle sympathetic nerve activity (MSNA), heart rate, and blood pressure were analyzed during slow respiration (0.1 Hz). Peak amplitude and phase were calculated from a cosine function fitted with 0.1 Hz by using the least squares method. The latency of the pressor response to MSNA, defined as lag time from the peak of MSNA to diastolic blood pressure, was significantly longer in the aged than the young group (7.1 +/- 0.3 vs. 5.4 +/- 0.4 s; P < 0.01). The extent of pressor response to MSNA, defined as diastolic blood pressure rise in response to increase in total MSNA, was significantly lower in the aged than the young group (0.038 +/- 0.006 vs. 0.099 +/- 0.024 mmHg/unit, P < 0.001). These results suggest that alpha-receptor-mediated vasoconstrictive responses to MSNA may be attenuated in the elderly.

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