Hot Flashes and Neurovascular Function in Women

Women who experience hot flashes are at greater risk for hypertension and other cardiovascular disease. Neurovascular control mechanisms are likely to play an important role in this relationship. As such, these studies are designed to provide a major step forward in understanding the link between hot flashes and neurovascular dysfunction and, by extension, cardiovascular disease in women.

Hot Flash frequency will be assessed in the study subjects during a screening period. Participants can then chose to participate 1 or 2 study visits- Protocol 1: Microvascular function and/or Protocol 2: Autonomic function

Muscle sympathetic nerve activity will be measured continuously at baseline and in response to sympathoexcitatory stressors, including a Valsalva maneuver, isometric handgrip exercise, a cold pressor test, and stepped hypercapnia.

Sodium nitroprusside, used to test endothelium-independent vasodilation, will be infused through a brachial artery catheter at 0.25, 0.5, 1.0 and 2.0 ug/100ml tissue/min.

Acetylcholine, used to test endothelium-dependent vasodilation, will be infused through a brachial artery catheter at 1.0, 2.0, 4.0, and 8.0 μg/100ml tissue/min

Terbutaline, a β2-Adrenergic selective agonist, will be infused through a brachial artery catheter at 0.1, 0.5, 1.0, and 2.0 μg/100ml tissue/min.

Norepinephrine, an α-adrenergic vasoconstricting agent, will be infused through a brachial artery catheter at 1.0, 2.0, 4.0, and 8.0 ng/100ml tissue/min

Change in forearm vascular conductance with intra-arterial drug infusions. Vascular conductance is an index of vascular tone and is assessed using a technique called venous occlusion plethysmography

Continuous measurement of vascular conductance during infusion of each drug- 3min at baseline and at each drug dose (~60min total of continuous forearm vascular conductance measurements)

Continuous measurement of muscle sympathetic nerve activity at rest and in response to stressors (~75min of continuous data collection once a sympathetic nerve signal is found)

Inclusion Criteria: Non-smokers. Non-obese. Have at least one ovary. Free from cardiovascular disease. Not taking medications influencing cardiovascular function. Exclusion Criteria: - None.