A PET Study in Healthy Volunteers

Inclusion Criteria: 1. Healthy as determined by a responsible physician 2. Male subjects between 25 and 55 years of age. 3. Male subjects must agree to use one of the contraception methods listed 4. Capable of giving written informed consent Exclusion Criteria: 1. The subject has a positive pre-study drug/alcohol screen 2. The subjects is using or has used regular prescription or non-prescription drugs 3. Current or recent (within one year) gastrointestinal disease 4. A screening ECG with a QTc value of \>450msec and/or a PR interval outside the range 120 to 200msec or an ECG that is not suitable for QT measurements 5. Pulse rate \<50 or \>100 bpm OR a systolic blood pressure \>140 or \<100 OR a diastolic blood pressure \>90 or \<60. 6. History of long QT syndrome (personal or family) or other cardiac conduction disorder, or other clinically significant cardiac disease. 7. Any previous or current psychiatric diagnosis listed in DSM-IV Axis I or II 8. Any history of suicidal attempts, suicidal ideation or behaviour as assessed by appropriately trained study personnel. 9. History of alcohol dependence 10. The subject has participated in a clinical trial and has received an investigational product within the following time period prior to the first dosing day in the current study: 30 days, 5 half-lives or twice the duration of the biological effect of the investigational product (whichever is longer). 11. Exposure to more than four new chemical entities within 12 months prior to the first dosing day. 12. History of sensitivity to any of the study medications, or components thereof or a history of drug or other allergy that, in the opinion of the investigator or GSK Medical Monitor, contraindicates their participation. 13. Where participation in the study would result in donation of blood or blood products in excess of 550 mL within a 56 day period. 14. Previous inclusion in a research and/or medical protocol involving nuclear medicine, PET or radiological investigations with significant radiation burden 15. Family history of cancer 16. History of claustrophobia or subjects feeling that he will be unable to lie still on his back in the PET camera for a period of \~2 hours at a time. 17. History or presence of a neurological diagnosis 18. Presence of a cardiac pacemaker or other electronic device or ferromagnetic metal foreign bodies as assessed by a standard pre-MRI questionnaire. 19. Unwillingness or inability to follow the procedures outlined in the protocol. -