Inclusion Criteria:  healthy adult men and women; 18-45 years of age; BMI <30 kg/m2; non-pregnant/non-breastfeeding; non-smokers.  Exclusion Criteria:  Subjects will be excluded if they are:  taking any medications known to affect the cardiovascular or autonomic nervous system (e.g. alpha-blockers, beta-blockers, etc); Apnea Hypopnea Index >10 events/hr  Self-reported history of:  hepatic, renal, pulmonary, cardiovascular, or neurological disease; stroke or neurovascular disease; bleeding/clotting disorders; sleep apnea or other sleep disorders; diabetes; smoking; history of alcoholism or substance abuse; hypertension.