Inclusion Criteria:  Healthy on the basis of physical examination, medical history (screening only), vital signs, and electrocardiogram (ECG) performed at screening and admission to the study site on Day -1. Minor abnormalities in ECG, which are not considered to be of clinical significance by the investigator, are acceptable Body weight not less than 50 kilograms (kg) and body mass index (BMI; weight [kg]/height^2 [m^2]) within the range of 18.0 to 29.9 kilogram per meter square (kg/m^2) (inclusive) Blood pressure (after the participant is supine for 5 minutes) between 90 millimeters of mercury (mmHg) and 140 mmHg systolic, inclusive, and no higher than 90 mmHg diastolic at screening and Day -1 A 12-lead ECG consistent with normal cardiac conduction and function, at screening and Day -1, including: sinus rhythm; pulse rate between 40 and 100 beat per minutes (bpm), extremes included; QTc interval less than or equal to (<=) 450 milliseconds (ms) for men; QRS interval of less than (<) 120 ms; PR interval < 210 ms; morphology consistent with healthy cardiac conduction and function Non-smokers (not smoked for 3 months prior to screening)  Exclusion Criteria:  History of malignancy within 5 years before screening (exceptions are squamous and basal cell carcinomas of the skin, or malignancy, which is considered cured with minimal risk of recurrence) Known allergies, hypersensitivity, or intolerance to aticaprant or its excipients History of clinically significant (example: in the opinion of the investigator) drug and/or food allergies Participant has presence of left bundle branch block, atrioventricular block (second degree or higher), or a permanent pacemaker or implantable cardioverter defibrillator Anatomical (nasal) abnormalities which may make the placement of the nasoduodenal tube difficult (only for participants with duodenal sampling)