Imaging of Cannabinoid CB(1) Receptors Using [11C] MePPEP

This study will test a new radioactive tracer, [(11)C]MePPEP, for use in positron emission tomography (PET) imaging. The tracer is used to visualize cannabinoid receptors, proteins in the brain that mediate a variety of natural chemicals. These receptors may be important in behavioral diseases such as addiction, obesity and psychiatric diseases.

Healthy normal volunteers between 18 and 65 years of age may be eligible for this study.

Ten participants undergo whole body PET imaging to determine where the [(11)C]MePPEP tracer is distributed in the body in order to calculate radiation exposure from the tracer. Another 10 subjects undergo brain imaging with [(11)C]MePPEP to measure cannabinoid receptors in the brain.

All participants are evaluated with a medical history and physical examination, blood and urine tests and an electrocardiogram (ECG) before scanning. They then have a PET scan. For this procedure, a catheter (plastic tube) is placed in a vein in the arm through which the tracer is injected. A special mask is fitted to the head and attached to the bed to help keep the head in place during the scan. Subjects undergoing brain imaging also have a catheter placed in an artery in the wrist from which blood samples are collected during the procedure. The scan lasts about 2 to 2.5 hours.

Subjects undergoing brain imaging also have magnetic resonance imaging (MRI) within 1 year of the PET scan. For MRI, the subject lies on a bed that moves into the tubular scanner, wearing earplugs to protect the ears from loud noises that occur during the scan. The procedure takes about 1 hour.