MK-8189 Multiple Dose Study in Healthy Volunteers and Schizophrenia Participants (MK-8189-003)

MK-8189, oral, 2 mg and/or 10 mg tablets, taken QD for a total daily dose of 2 mg, 4 mg, 8 mg, 10 mg, 12 mg, 14 mg, 16 mg, 20 mg, or 40 mg

Placebo matching oral 2 mg and/or 10 mg MK-8189 tablets, taken QD

For Part 2 only: participants need to be on monotherapy with an atypical antipsychotic medication (eg, Olanzapine, Quetiapine, Paliperidone, Asenapine, Iloperidone, Aripirprazole, Lurasidone, Risperidone \[not to exceed daily dose of 6 mg\], or Ziprasidone.) The participant should be on a stable and well tolerated treatment regimen for at least 2 months prior to screening. NOTE: Clozapine is not allowed.