Three panels, each consisting of either 8 or 9 participants (8 healthy young males in Panel A and Panel B; and 9 participants with mild to moderate hypertension in Panel C) will be randomized to receive either MK-8266 or matching placebo in either a 6:2 ratio (Panel A and Panel B) or 6:3 ratio (Panel C), respectively, in up to 5 treatment (1 to 5) periods in Panel A and up to 4 treatment (1 to 4) periods in Panel B and Panel C. In all panels, doses will be escalated in a rising, fixed sequence. Some participants took study drug after fasting and some with food.