• INCLUSION CRITERIA:

The subjects are healthy volunteers 18 years or older who are not pregnant or lactating.

EXCLUSION CRITERIA:

Minors younger than 18 years old are excluded.

A candidate subject is excluded if, in the judgment of the Principal Investigator, Protocol participation would place the subject at substantially increased acute medical risk. A candidate subject is excluded if, in the opinion of the Principal Investigator, the medical risk outweighs the potential scientific benefit.

A candidate subject is excluded if there is a disqualifying condition. Examples of disqualifying conditions are hepatic failure, a history of tachyarrhythmias or heart block, symptomatic congestive heart failure, severe anemia, psychosis, refractory ventricular arrhythmias, symptomatic coronary heart disease, diabetes mellitus, or hyperthyroidism. Abnormal screening results may exclude further participation, at the discretion of the Principal Investigator.

Subjects will be excluded from further participation and referred for medical management, if the systolic blood pressure during supine rest is greater than or equal to 160 mm Hg or diastolic blood pressure greater than or equal to 105 mm Hg. Hypertensives are excluded from the part of the study about coffee drinking.

Alcohol addiction.

A candidate subject is excluded if clinical considerations require that the patient continue treatment with a drug likely to interfere with the scientific results. Examples are acetaminophen, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, adrenoceptor agonists or antagonists, anticoagulants, anticonvulsants, antipsychotics, calcium channel blockers, hypoglycemic agents, digoxin, dopaminergic drugs, monoamine oxidase inhibitors, oral contraceptives, sedatives, steroids, and tricyclic antidepressants. Patients are not to discontinue any medications, just to participate in this study.

Subjects in whom we feel it would be difficult to insert a catheter into a vein may be excluded.

Pregnant or lactating women are excluded. To exclude pregnancy, women with child bearing potential have blood testing for pregnancy, with negative results obtained within 1 day of each day of testing.