The purpose of this study is to learn the effects of genetic make up on response to the drugs atropine and propranolol, to examine how changes in heart rate and blood pressure can be measured, and to test a new statistical analysis method.

Healthy volunteers will be recruited and screened for eligibility. Participants will be placed into three possible groups based on genetic information obtained during screening. Rolling admissions will continue until at least 10 participants have been recruited for each genetic group. Participants will be randomly assigned to receive either the control (propranolol and saline) or combined drug (propranolol and atropine) treatment in a non-blinded fashion. The participant will return over one week later to receive the alternate treatment. Continuous heart rate/blood pressure data will be recorded until the end of the study period. Respiratory rate will be maintained at a fixed rate. Participants will undergo an orthostasis task, receive the drug or control infusions, and blood samples will then be obtained to determine drug concentrations at specific time intervals. Several relatively new mathematical techniques will be applied to the data.

Inclusion Criteria:

• Healthy male and female volunteers
• Ages 21-40
• Body Mass Index >18.0 and <27.0

Exclusion Criteria:

• History of any chronic illnesses including cardiac diseases and bleeding problems
• Drug use of any kind
• Participation in any clinical trial within the last month
• Tobacco use and/or alcohol abuse
• Use of dietary supplements and unwillingness to refrain