The increase in skin blood flow in response to rapid local heating of the skin (i.e., cutaneous vasodilation) is commonly used to assess nitric oxide (NO)-dependent dilation and overall microvascular function. Historically, rapid local heating to 42°C was considered the standard approach for these assessments. More recently, many investigators have adopted rapid local to 39°C instead, based on its larger dependency on NO and therefore improved ability to quantify NO-dependent dilation without the use of pharmacological techniques. However, to date, only one direct methodological comparison between these protocols has been performed.

In this study, the investigators use the blood vessels in the skin as a representative vascular bed for examining mechanisms of microvascular dysfunction in humans. Using a minimally invasive technique (intradermal microdialysis for the local delivery of pharmaceutical agents) they examine the blood vessels in a nickel-sized area of the skin in young adults ages 18 - 30 years old. Local heating of the skin at the microdialysis sites is used to explore differences in mechanisms governing microvascular control. As a compliment to these measurements, the investigators also have participants fill out a variety of surveys to assess things such as sleep quality, physical activity, daily stressors, etc.

Inclusion Criteria:

• men and women
• 18-30 years of age

Exclusion Criteria:

• Current or recent (within 8 wks) use of medication that could conceivably alter microvascular function [including (but not limited to) stimulants, antihypertensives, HMG-CoA reductase inhibitors]
• Changes or alterations in medication status (starting a new, additional, or different medication or changing the dose of a current medication)
• Unstable or diagnosed chronic clinical disease, including cardiovascular, metabolic, renal, hepatic, autonomic, autoimmune, or dermatological disease (e.g., hypertension, heart disease, diabetes, hyperlipidemia, psoriasis)
• Body mass index <18.5 or >35 kg/m2
• Pregnancy (including a positive urine pregnancy test) or breast-feeding
• Known allergies to pharmacological agents or study drugs
• Non-English-speaking. Participants need to understand English to follow instructions and comply with procedures conducted during the screening and experimental visits.