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Effects of yohimbine on human sympathetic nervous system function
M M Murburg1, E C Villacres, G N Ko
1Geriatrics Research, Education, and Clinical Center, Seattle Veterans Administration Medical Center, Washington.
The Journal of Clinical Endocrinology and Metabolism
|October 1, 1991
Summary
Yohimbine, an alpha 2-adrenergic antagonist, increases plasma norepinephrine (NE) by enhancing NE release from sympathetic nerves. This study confirms yohimbine
Area of Science:
- Neuroendocrinology
- Pharmacology
- Human Physiology
Background:
- Alpha 2-adrenergic receptor antagonist yohimbine is a common neuroendocrine probe.
- It is widely assumed to elevate plasma norepinephrine (NE) by augmenting sympathetic nervous system outflow.
Purpose of the Study:
- To investigate the mechanism by which yohimbine affects plasma NE levels.
- To determine if yohimbine alters NE kinetics (production and clearance) or epinephrine release.
Main Methods:
- Utilized a radioisotope dilution technique to measure NE kinetics in arterialized plasma.
- Administered oral yohimbine (20 or 40 mg) or placebo to healthy young men.
Main Results:
- Yohimbine induced dose-dependent increases in blood pressure, heart rate, and plasma NE.
- The rise in plasma NE resulted from increased NE appearance rate, not decreased clearance.
- A dose-dependent increase in plasma epinephrine was observed, which was not detected in previous venous plasma studies.
Conclusions:
- Yohimbine elevates plasma NE by increasing the rate of NE release from sympathetic nerves.
- Yohimbine likely stimulates epinephrine release from the adrenal medulla.