Related Experiment Videos
Orthostatic hypotension: a posture-induced hyperdopaminergic state.
The American Journal of the Medical Sciences
|January 1, 1985
Summary
Orthostatic hypotension may be caused by excessive dopamine release in response to standing, potentially a compensatory mechanism. This dopamine increase may worsen hypotension through vasodilation and natriuresis.
Area of Science:
- Neuroscience
- Cardiovascular Physiology
- Endocrinology
Background:
- Orthostatic hypotension (OH) is characterized by a significant drop in blood pressure upon standing.
- The role of dopaminergic mechanisms in OH pathophysiology remains incompletely understood.
- Autonomic nervous system dysfunction is implicated in OH, but specific neurotransmitter roles require further elucidation.
Purpose of the Study:
- To investigate the involvement of dopaminergic pathways in the development of orthostatic hypotension.
- To compare the neurochemical and physiological responses to postural changes in patients with OH and healthy controls.
- To elucidate the relationship between dopamine, norepinephrine, and hormonal responses during orthostatic stress.
Main Methods:
- Radioenzymatic determination of free and sulfated catecholamines (dopamine and norepinephrine) in plasma and urine.
- Comparison of postural responses (blood pressure, heart rate, diuresis, natriuresis) between 20 OH patients and a control group.
- Categorization of OH patients into normo-/hyperadrenergic and hypoadrenergic subgroups based on norepinephrine levels.
Main Results:
- Patients with OH showed an increase in total plasma dopamine (DA) upon assuming an upright posture, unlike controls.
- Hypoadrenergic OH patients exhibited more severe hypotension, reduced diuresis/natriuresis, and altered dopamine/norepinephrine ratios compared to normo-/hyperadrenergic patients and controls.
- Normo-/hyperadrenergic OH patients had elevated plasma renin activity (PRA) and aldosterone in the upright position.
Conclusions:
- Excessive free dopamine release in response to upright posture may contribute to orthostatic hypotension, possibly as a compensatory autonomic response.
- Rapid sulfoconjugation of dopamine might mask its active form, detectable as dopamine sulfate.
- Findings support the hypothesis that excessive dopamine release, with its vasodilating and natriuretic effects, can perpetuate orthostatic hypotension.