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Increased plasma norepinephrine response to yohimbine in elderly men
E C Petrie1, E R Peskind, D J Dobie
1Department of Psychiatry and Behavioral Sciences, University of Washington School of Medicine, Seattle, USA. petrie.eric@seattle.va.gov
Summary
Aging increases sympathetic nervous system outflow, indicated by greater plasma norepinephrine responses to yohimbine in older men. This heightened outflow is not due to reduced alpha-2 adrenoreceptor feedback inhibition.
Area of Science:
- Gerontology
- Neuroscience
- Cardiovascular Physiology
Background:
- Aging impacts the sympathetic nervous system (SNS) and adrenomedullary outflow.
- Plasma norepinephrine (NE) and epinephrine (EPI) responses to pharmacological agents can estimate these changes.
Purpose of the Study:
- To investigate the effects of aging on SNS and adrenomedullary outflow.
- To compare NE and EPI responses to yohimbine and clonidine in young versus older men.
Main Methods:
- Healthy young (n=18, age 26±1) and older (n=5, age 74±1) men received yohimbine, clonidine, or placebo.
- Plasma NE and EPI levels were measured via radioenzymatic assay at baseline and 30, 60, 90 minutes post-administration.
Main Results:
- Older men exhibited greater plasma NE increases after yohimbine compared to young men.
- Baseline plasma NE and systolic blood pressure were higher in older men.
- Plasma NE and EPI responses to clonidine did not differ between age groups.
Conclusions:
- Human aging is associated with increased sympathetic nervous system outflow.
- This increase is independent of reduced alpha-2 adrenoreceptor-mediated feedback inhibition.