Glutamate is a natural neurotransmitter, or chemical messenger, that is essential for normal brain function. Yet too much glutamate can overexcite neurons and even cause them to die. Such "excitotoxicity" may play a role in Alzheimer's disease.

One of the main cellular receptors, or "docking sites," for glutamate is the metabotropic glutamate receptor type five (mGLUR5). In studies of autopsied brains from people with memory loss, researchers have found elevated levels of mGLUR5. This finding indicates that the brains suffered high levels of glutamate and related excitotoxicity.

Pedro Rosa-Neto, M.D., Ph.D., and colleagues plan to search for elevated mGLUR5 levels in the brains of individuals with Alzheimer's disease. The researchers will use a novel imaging technique for their effort. First, they will administer a compound into the brains of their participants. This compound binds to mGLUR5 and "highlights" it on a brain scan. The investigators will then use a procedure called positron emission tomography (PET) to take the brain scans. Analysis of these scans could elucidate the links between brain levels of mGLUR5 and Alzheimer development.

Dr. Rosa-Neto and colleagues believe their study may lead to a new method for diagnosing early Alzheimer's disease.