The purposes of this study are to measure the whole-body distribution and radiation dosimetry of [18F]-JNJ-70099731 (Part A), to measure the uptake, distribution, and clearance (CL) of [18F]-JNJ-70099731 by Positron Emission Tomography (PET) and to model tissue specific kinetics of [18F]-JNJ-70099731 with the appropriate input function (IF) (Part B), and to measure participant test-retest variability in the distribution of [18F]-JNJ-70099731 by comparing PET scans obtained at least 1 week apart (Part C) in the brain of healthy male participants.

Inclusion Criteria:

• Body mass index (BMI) between 18 and 32 kilogram per meter square (kg/m^2) inclusive
• Participant must be healthy on the basis of physical and neurological examination, medical history, clinical laboratory tests, vital sign (VS), and 12-lead electrocardiogram (ECG) performed at screening. Minor deviations in ECG (example, first-degree atrioventricular block), which are not considered to be of clinical significance to the investigator, are acceptable
• Participant must sign an informed consent form (ICF) indicating that he understands the purpose of and procedures required for the study and is willing to participate in the study
• Part B & Part C only: Participant is willing to allow the investigators to place an arterial catheter in the radial artery. Suitability for arterial catheter placement will be assessed via physical examination (modified Allen Test on both hands). Participant should not be allergic to local anesthetics for catheter placement
• Participant must agree not to donate sperm during the study and for a minimum of 1 spermatogenesis cycle (defined as approximately 90 days) after receiving the last dose of study intervention. If a participant is sexually active with a woman, he should agree to the following: a) If it concerns a woman of childbearing potential and the participant has not had a vasectomy, the participant must agree to use a condom and make sure his female partner is using a highly effective method of birth control during the study and for a minimum of 90 days after the last dose of study intervention; b) If it concerns a woman of nonchild bearing potential or who is pregnant or has been sterilized and the participant has not had a vasectomy, the participant must agree to use a condom for the given period; c) If the participant has had a vasectomy, he should agree to use a condom when being sexually active with a woman of childbearing potential. Contraceptive use by men or women should be consistent with local regulations regarding the use of contraceptive methods for participants participating in clinical studies

Exclusion Criteria:

• Clinically significant abnormal values for hematology, clinical chemistry, coagulation or urinalysis at screening. It is expected that laboratory values will generally be within the normal range for the laboratory, though minor deviations, which are not considered to be of clinical significance to the Principal Investigator, are acceptable
• Clinically significant abnormal physical and neurological examination, VS or 12-lead ECG at screening or before study intervention administration
• History of or current significant medical illness including (but not limited to) cardiac arrhythmias or other cardiac disease, coagulation abnormalities, or other conditions that the Investigator considers should exclude the participant and preclude their ability to participate in study procedures. Participants with a history significant liver or renal disease, or difficulty in urination, which could affect the metabolism and elimination of the radiotracer or radiometabolites should be excluded. Participants with a history of epilepsy or seizures of significance or unexplained black-outs or loss of consciousness should also be excluded
• Exposed to greater than (>)1 millisievert (mSv) of ionizing radiation participating as a participant in research studies and/or at work in the 12 months before the start of this study, to the participant's knowledge
• Serology positive for hepatitis B surface antigen (HBsAg), hepatitis C virus (HCV) antibodies or human immunodeficiency virus (HIV) antibodies

The data sharing policy of the Janssen Pharmaceutical Companies of Johnson & Johnson is available at www.janssen.com/clinical-trials/transparency. As noted on this site, requests for access to the study data can be submitted through Yale Open Data Access (YODA) Project site at yoda.yale.edu.