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Norepinephrine-induced plasma dopamine decrease in man: pharmacological evidence of the involvement of alpha
N R Musso1, R Gianrossi, C Vergassola
1Department of Internal Medicine, University of Genoa, Italy.
Journal of Hypertension
|September 1, 1992
Summary
Norepinephrine infusion decreases plasma dopamine levels, an effect mediated by alpha 2-adrenoceptors. This finding suggests norepinephrine acts as a hormone influencing dopamine release.
Area of Science:
- Endocrinology
- Neuroscience
- Pharmacology
Background:
- Norepinephrine is a key neurotransmitter and hormone.
- Dopamine plays crucial roles in physiological processes.
- The interaction between norepinephrine and dopamine levels requires further elucidation.
Purpose of the Study:
- To investigate the effect of intravenous norepinephrine infusion on plasma dopamine levels in humans.
- To determine the role of dopamine-2 and alpha 2-receptors in mediating norepinephrine's influence on dopamine.
Main Methods:
- Seven healthy subjects received norepinephrine infusions.
- Plasma catecholamine levels were measured before and after administration of domperidone (dopamine-2 antagonist) and yohimbine (alpha 2-antagonist).
Main Results:
- Both domperidone and yohimbine increased plasma norepinephrine and dopamine levels.
- Norepinephrine infusion significantly decreased plasma dopamine.
- Yohimbine fully blocked the norepinephrine-induced dopamine decrease, while domperidone only partially did.
Conclusions:
- Norepinephrine can function as a hormone at concentrations as low as 450 pg/ml.
- The decrease in plasma dopamine induced by norepinephrine is primarily mediated by alpha 2-adrenoceptors.
- This mechanism may explain physiological dopamine level changes observed in the upright position.