Genetic Variation in Platelet Aggregation

There is a marked diurnal fluctuation in the occurrence of acute myocardial infarction and
sudden death, with peak incidences occurring in the early morning. Platelet aggregation has
also been shown to increase in the early morning. The investigators will test the hypothesis
that ADRA2A genetic variation, specifically haplotype 4, affects platelet aggregation. The
investigators will compare diurnal platelet aggregation in haplotype 4 subjects with subjects
in the other haplotype families. In addition, the investigators will compare platelet
aggregation after the cold pressor test in haplotype 4 with the other haplotype families.

Inclusion Criteria:

- Men and women aged 18 - 45 years inclusive.

- Women of the above age will be studied between day 1 and day 14 of a normal menstrual
cycle.

- Subjects must be willing to give informed consent for the study and able to adhere to
the study diet and study procedures.

- Subjects and immediate extended family up till grandparents will be Caucasians or
African Americans only.

- Subjects will be free of any clinically significant disease.

- Clinical laboratory test (CBC, blood chemistry) will be within acceptable limits.

Exclusion Criteria:

- Subjects who have taken any antiplatelet, anticoagulant or procoagulant medicines
within the last three weeks preceding the study.

- Subjects who have taken medications (including over the counter medications) other
than oral contraceptives in the past two weeks.

- Subjects who smoke or have smoked in the past 3 months.

- Subjects who are presently or were formerly a narcotic addict or alcoholic.

- Females with a positive pregnancy test.

- Females who are breast feeding.