Inclusion Criteria:

1. Ages 18 to 65 years old.

2. Smoke 10 cigarettes per day for the previous 6 months.

3. Weigh less than 300lbs (due to limitations of the PET and MRI scanners).

Exclusion Criteria:

1. Smoking behavior:

1. Current enrollment or plans to enroll in a smoking cessation program, or use
other smoking cessation medications in the next 2 months.

2. Provide a CO reading of less than 10 ppm at medical screening.

2. Alcohol/Drugs:

1. History of substance abuse and/or currently receiving treatment for substance
abuse (e.g., alcohol, opioids, cocaine, marijuana, or stimulants).

2. Positive drug screen at any of the sessions (see page 8 for list of drugs and/or
contra-indicated medications).

3. Current alcohol consumption that exceeds 25 standard drinks/week.

4. Providing a breath alcohol concentration (BrAC) reading of greater than or equal
to 0.01 at any session.

3. Medical:

1. Women who are pregnant, planning a pregnancy, or lactating; all female subjects
shall undergo a serum pregnancy test at the medical screening session and urine
pregnancy tests at the two PET scans and MRI scan.

2. Women of child-bearing age must agree in writing to use an approved method of
contraception or agree to abstain from sexual intercourse

3. History or current diagnosis of the following psychiatric diagnoses identified
by the MINI (Mini International Neuropsychiatric Interview) such as psychosis,
bipolar disorder, schizophrenia, major current depression, or any Axis 1
disorder

4. Self-report of serious or unstable disease within the past 6 months (e.g.,
cancer [except melanoma], HIV/AIDS, stroke, angina, coronary disease, heart
attack).

5. History of epilepsy or a seizure disorder.

6. Any medical or neurological condition that might interfere with the distribution
of the radiotracer as determined by the study M.D.

4. Medication:

a. Current use or recent discontinuation (within last 14-days) of the following
medications:

- Any form of smoking cessation medication (Zyban, Wellbutrin, Wellbutrin SR,
Chantix, NRT);

- Recent (within last 14 days) or planned use of psychotropic medications
(anti-psychotics, anti-depressants, anti-anxiety, anti-panic medications, mood
stabilizers, opioids, and stimulants).

- Participants shall be instructed to refrain from using any study prohibited
drugs (note - participants are allowed to take prescription medicines not in the
exclusion list) throughout their participation in the study.

5. Imaging-Related Exclusion Criteria:

1. Self-reported history of head trauma or brain (or CNS) tumor.

2. Self-reported history of claustrophobia (contraindicated for PET and MRI).

3. Having a cochlear implant or wearing bilateral hearing aids.

4. Self-reported use of pacemakers, certain metallic implants, or presence of metal
in the eye as contraindicated for MRI.

5. History of gunshot wound.

6. Circumstances or conditions that may interfere with magnetic resonance imaging
(MRI)

7. Inability to complete the baseline study procedures within four hours and/or
correctly, as determined by the PI.