P-glycoprotein Function in Brain Diseases

Study Summary

This study will measure the function of a protein called P-glycoprotein (P-gp), which is found at the blood-brain barrier, a membrane that normally prevents toxic material from entering the brain. Impaired P-gp function may allow toxins to enter the brain and cause some people to develop certain brain diseases. Healthy subjects and people with Alzheimer s disease, Parkinson s disease or frontotemporal dementia who are 35 years of age or older and in overall good health may be eligible for this study. Participants undergo the following procedures during three outpatient visits to the NIH Clinical Center: * Medical history, psychological evaluation, physical examination and blood and urine tests, including tests for illegal and addictive drugs. * PET scan: This test uses small amounts of a radioactive chemical called a tracer that labels active areas of the brain so the activity can be seen with a special camera. Before starting the scan, a catheter (plastic tube) is placed in a vein in the arm to inject the tracer. The subject lies on the scanner bed, with a special mask fitted to the head and attached to the bed to help keep the head still during the scan so the images obtained are clear. A brief initial scan is done to calibrate the scanner. Then, a radioactive tracer called \[(15)O\]H(2)O is injected into the catheter and the PET camera takes pictures of blood flow to the brain for about 60 seconds. Next, another tracer, \[(11)C\]dLop, is injected into the catheter and pictures are taken for about 2 hours to determine how much of this tracer is allowed to enter the brain. * Magnetic resonance imaging (MRI): This procedure is done within 1 year (before or after) the PET scan. MRI uses a magnetic field and radio waves to produce images of the brain. For this procedure, the patient lies on a table that can slide in and out of the scanner (a tube-like device), wearing earplugs to muffle loud knocking and thumping sounds that occur during the scan.