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Plasma norepinephrine in the evaluation of baroreceptor function in humans
Hypertension (Dallas, Tex. : 1979)
|July 1, 1982
Summary
Plasma norepinephrine levels accurately reflect baroreceptor-mediated sympathetic activity. The sympathetic nervous system shows a greater response to a drop in blood pressure than to a rise, as indicated by norepinephrine changes.
Area of Science:
- Cardiovascular Physiology
- Autonomic Nervous System Regulation
Background:
- Baroreceptors are crucial for short-term blood pressure regulation.
- Sympathetic vasomotor activity influences blood pressure and heart rate.
- Plasma norepinephrine is a marker of sympathetic nervous system activity.
Purpose of the Study:
- To evaluate plasma norepinephrine as an indicator of baroreceptor-mediated sympathetic vasomotor activity.
- To compare the sympathetic response to blood pressure reduction versus elevation.
Main Methods:
- Seven healthy volunteers underwent controlled hypotension using sodium nitroprusside and hypertension using phenylephrine.
- Blood pressure, heart rate, and plasma norepinephrine levels were measured during infusions.
- Changes in plasma norepinephrine were correlated with blood pressure and heart rate alterations.
Main Results:
- Both sodium nitroprusside and phenylephrine induced significant changes in blood pressure and heart rate.
- Plasma norepinephrine increased during hypotension and decreased during hypertension.
- The increase in plasma norepinephrine during blood pressure reduction was significantly greater than the decrease during pressure elevation.
Conclusions:
- Plasma norepinephrine measurement is a valid method for assessing baroreceptor-mediated sympathetic vasomotor activity.
- The sympathetic nervous system exhibits a more pronounced response to a decrease in blood pressure compared to an increase.
- Findings support the role of sympathetic outflow in blood pressure homeostasis.