Neurobiological Mechanisms in Panic Disorder

This study will examine brain and noradrenaline function in panic disorder. Noradrenaline is a brain chemical that is involved in the regulation of emotion, anxiety, sleep, stress hormones such as cortisol, and other body functions that are disturbed in panic disorder. Healthy normal volunteers and patients with panic disorder between 18 and 60 years of age may be eligible for this study. Candidates are screened with psychiatric and medical histories, a physical examination, blood and urine tests, and an electrocardiogram. Participants undergo the following tests and procedures:

• Blood draw to obtain DNA for genetic studies of panic disorder - particularly of a gene that helps control noradrenaline activity - and to grow cell lines that can be frozen and used for future research on the disorder.
• Magnetic resonance imaging: MRI uses a magnetic field and radio waves to produce images of body tissues and organs. For this procedure, the subject lies on a table that is moved into the scanner (a narrow cylinder), and wears earplugs to muffle loud knocking and thumping sounds that occur during the scanning process. The procedure lasts about 60 minutes, during which the patient is asked to lie still for 10 to 15 minutes at a time.
• Yohimbine injection with PET scanning: Catheters (plastic tubes) are placed in two veins, one to administer yohimbine, a drug that increases noradrenaline activity in the body for about 60 minutes, and one to draw blood samples. Yohimbine often causes temporary trembling, goosebumps, and clammy palms, and may cause emotions such as elation, anxiety, panic attacks, or depression. During yohimbine administration, subjects undergo positron emission tomography (PET) scanning. PET uses small amounts of a radioactive chemical called \[fluoro-18\]-fluorodeoxyglucose that "labels" active areas of the brain, showing patterns of glucose (sugar) metabolism. For the procedure, the subject lies on the scanner bed, with a special mask fitted to his or her head and attached to the bed to help keep the head still. A brief "transmission" scan is done just before the radioactive tracer is injected in order to calibrate the scanner. After the tracer is injected through the catheter, pictures are taken for about an hour, while the subject lies still on the scanner bed.
• Saline injection with PET scanning: The procedure is the same as that described above, except a saline solution is administered as placebo instead of yohimbine.