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Physiological arginine vasopressin levels do not enhance baroreflex function in normal humans
1Hennepin County Medical Center, Minneapolis, Minnesota.
The American Journal of Physiology
|June 1, 1994
Summary
Physiological increases in arginine vasopressin (AVP) did not alter sympathetic nervous system activity or baroreflex responses in humans. This study found no significant effects of AVP on heart rate or norepinephrine spillover during tilt tests.
Area of Science:
- Cardiovascular Physiology
- Neuroendocrinology
Background:
- Arginine vasopressin (AVP) can modulate baroreflex activity, but its effects on human sympathetic nervous system activity at physiological levels are unclear.
- Previous studies suggest pharmacological AVP doses decrease sympathetic activity, but the impact of smaller increases remains unknown.
Purpose of the Study:
- To investigate the effects of physiological AVP increases on basal sympathetic activity in humans.
- To determine if AVP influences baroreflex responses during unloading (head-up tilt) and loading (head-down tilt with phenylephrine).
Main Methods:
- Healthy human subjects received infusions of AVP or a vehicle control in a double-blind manner.
- Systemic venous norepinephrine (NE) spillover was measured to assess sympathetic activity.
- Cardiovascular and sympathetic responses were evaluated during supine rest, head-up tilt, and head-down tilt with phenylephrine infusion.
Main Results:
- AVP administration did not affect basal sympathetic nervous system activity, as measured by NE spillover.
- Physiological AVP levels did not alter heart rate, forearm vascular resistance, or NE spillover responses during baroreceptor unloading (head-up tilt).
- AVP did not augment or restrain cardiovascular and sympathetic responses during baroreceptor loading maneuvers.
Conclusions:
- Physiological increases in plasma AVP do not significantly impact basal sympathetic nervous system activity in normal humans.
- AVP at physiological concentrations does not modulate baroreflex control of heart rate and sympathetic activity during unloading or loading conditions.