The purpose of this study is to evaluate the relationship between plasma drug levels and receptor binding in brain using PET; and to evaluate safety and tolerability after a single administration of PF-04995274 in healthy volunteers.

Inclusion Criteria:

• healthy male and/or female subjects of nonchildbearing potential between the ages of 18 and 55 years, inclusive

Exclusion Criteria:

• Evidence or history of clinically significant hematological, renal, endocrine, pulmonary, gastrointestinal, cardiovascular, hepatic, psychiatric, neurologic, or allergic disease.
• History of regular alcohol consumption exceeding 7 drinks/week for females or 14 drinks/week for males (1 drink = 5 ounces (150 mL) of wine or 12 ounces (360 mL) of beer or 1.5 ounces (45 mL) of hard liquor) within 6 months of screening
• Fulfillment of any of the MRI contraindications on the standard radiography screening questionnaire