The purpose of the study is to evaluate the effect of ORM-12741 on receptor occupancy by positron emission tomography with different doses and plasma concentrations. The pharmacokinetic profile and safety will also be evaluated.

Inclusion Criteria:

• Good general health ascertained by detailed medical history and physical examination
• Males between 18 and 45 years
• Body mass index (BMI; weight/height2) between 18-30 kg/m2
• Weight 55-95 kg

Exclusion Criteria:

• Evidence of clinically significant cardiovascular, renal, hepatic, haematological, gastro-intestinal, pulmonary, metabolic-endocrine, neurological, urogenital or psychiatric disease as judged by the investigator
• Any condition requiring regular concomitant medication including herbal products or likely to need any concomitant medication during the study
• Regular consumption of more than 21 units of alcohol per week (1 unit = 4 cl spirits, about 13 g of alcohol).
• Current use of nicotine-containing products more than 5 cigarettes or equivalent/day
• Inability to refrain from using nicotine-containing products during the stay at the study centre
• Inability to refrain from consuming caffeine-containing beverages during the stay at the study centre e.g. propensity for headache when refraining from caffeine-containing beverages
• Blood donation or loss of significant amount of blood within 3 months prior to the screening visit
• Abnormal 12-lead electrocardiogram (ECG) finding of clinical relevance
• Any abnormal value of laboratory, vital signs, or physical examination, which may in the opinion of the investigator interfere with the interpretation of the test results or cause a health risk for the subject if he takes part into the study
• Anatomical abnormality in brain MRI which may in the opinion of the investigator interfere with the interpretation of the PET results
• Participation in another clinical drug study within 3 months prior to the start of this study or earlier participation in a clinical study with ORM-12741
• Participation in a prior PET study
• Any contraindication to MRI of the brain