Pharmacological Studies with Positron Emission Tomography

Positron emission tomography (PET) scanning of the brain had its origins in the measurement of regional blood flow and substrate metabolism. While these types of measurements continue to play an active role in the localization of brain function and in the clinical management of patients with diseases such as epilepsy, brain tumor, and dementia, the flow metabolism methods have limitations. The results of blood flow functional activation studies have provided a wealth of information on regional brain activation following sensory and cognitive stimuli, but mechanistic information regarding the functional role of neurotransmitters, neuroreceptors, and other neuromarkers in increasing or decreasing neuronal activity is not provided. Similarly, measurement of regional brain metabolism is useful for identifying and localizing functional abnormalities, differential diagnosis, and following the affects of treatment, but information regarding mechanisms of disease at a neurochemical level is lacking in these types of studies. For example, epilepsy is known to be associated with specific patterns of abnormal regional glucose metabolism, but epilepsy is not a disorder of altered carbohydrate metabolism. Rather, there are a series of inhibitory and excitatory neurotransmitters and their receptors that are thought to play a role in the origin of seizures.