Inclusion Criteria:

1. Signed written informed consent to participate in the study.
2. Age: 18 – 55
3. If female, non-pregnant, non-nursing with a negative serum pregnancy test and using an adequate form of birth control.
4. Supine and standing blood pressure within the range 110/60 to 150/90 mmHg.
5. Heart rate, after resting for 5 minutes, within the range 46-90 beats/min.
6. Subjects who are within 20% of the ideal weight for height as
7. Right handed.

Exclusion Criteria:

1. Diagnosis of any psychotic disorder, bipolar disorder, severe depression, severe anxiety, or Autism. Subjects with mild mood, oppositional, conduct, and anxiety disorders may be permitted to participate if considered appropriate by the investigator.

2. Scores of Baseline Scales:

   Hamilton Depression Scale > 17 (out of a possible 67 on the 21-item scale)[18] Beck Depression Inventory > 19 (out of a possible 63 on the 21-item scale)[19] Hamilton Anxiety Scale > 21 (out of a possible 56 on the 14-item scale) [20]

3. Tics or Tourette’s Syndrome.
4. History of head trauma with loss of consciousness, organic brain disorders, seizures, or neurosurgical intervention.
5. Any clinically significant chronic medical condition, in the judgment of the investigator.
6. Mental impairment as evidenced by an I.Q. <75.
7. Exposure to dopamine receptor antagonists within the previous three (3) months.
8. Exposure to radiopharmaceuticals within four (4) weeks prior to PET scan.
9. Subjects receiving psychotropic medication.
10. Any clinically significant abnormality in the screening laboratory tests, vital signs, or 11-lead ECG, outside of normal limits.

12. Any woman of childbearing potential who is seeking to become pregnant or suspects that she may be pregnant.

13. Subjects with a known recent history (within the past six (6) months) of illicit drug or alcohol dependence