Role of Substance P in Post-Traumatic Stress Disorder

This study will examine the role of substance P, a chemical messenger in the brain, in post-traumatic stress disorder (PTSD), a chronic anxiety disorder. PTSD can develop after exposure to a terrifying event or ordeal, such as a violent personal assault, natural or human-caused disaster, accident, or military combat. Substance P is a peptide that may be important in the response to certain psychiatric and neurological diseases and conditions, including anxiety. Healthy normal volunteers and people with PTSD who are between 18 and 65 years of age may be eligible for this study. Candidates are screened with a physical examination, blood and urine tests, pregnancy test for women who can become pregnant, and a neuropsychological evaluation. Participants undergo positron emission tomography (PET) and magnetic resonance imaging (MRI) scanning. An optional lumbar puncture (spinal tap) is also requested. PET Scanning PET uses small amounts of a radioactive chemical called a tracer that "labels" active areas of the brain. The tracer used in this study is \[18F\]SPA-RQ. For the procedure, the subject lies still on the scanner bed. A special mask is fitted to the head to help keep the subject's head still during the scan so the images will be clear. A 20-minute "transmission" scan is done before the radioactive tracer is injected to provide measures of the brain that will help in the precise calculation of information from subsequent scans. After the tracer is injected through a needle in the arm, pictures are taken continuously for about 2 hours. Then, 20- to 40-minute images are taken every hour until about 5 hours after the injection. MRI Scanning An MRI scan is scheduled at some time within 1 year of the PET scan. MRI uses a magnetic field and radio waves to obtain images of body tissues and organs. The subject lies still on a table inside the tunnel-like MRI scanner. Earplugs are worn to muffle loud noises that occur during the scanning. The maximum duration of the