Part I and Part II:

Has a history of stroke, seizures or major neurological disorder

Has a history of cancer

Has a history of any cardiovascular disease

Is unable to refrain from the use of any prescription or non-prescription drugs

Consumes excessive amounts of alcohol or caffeine

Has had major surgery, donated blood or participated in another investigational study in the past 4 weeks

Safety and Tolerability of MK-5478 in Participants With Hypertension (5478-001)