Functional Relevance of Dopamine Receptors in Healthy Controls and Patients With Schizophrenia: Characterization Through [11C]NNC-112 and [18F]Fallypride Positron Emission Tomography

Background: * Some illnesses, such as schizophrenia, have effects on brain cells called dopamine receptors, which are required for normal brain function. People with schizophrenia have difficulty thinking and experience hallucinations and delusions. Medications that change brain dopamine receptors can decrease these hallucinations and delusions. * The cause of schizophrenia and its association with brain dopamine receptors is not known but may be clarified by studying dopamine receptors in people who have dopamine disorders (such as schizophrenia) and those who do not. Researchers are interested in studying the dopamine system to gain a better idea of how dopamine disorders develop, which may lead to better medical care for people with schizophrenia. Objectives: \- To study the amount and distribution of two types of dopamine receptors. Eligibility: * Individuals between the ages of 18 and 60 who have schizophrenia. * Healthy volunteers between the ages of 18 and 90. Design: * Participants will undergo a full screening, with physical and psychological history, a neurological examination, and blood and urine samples. * Participants will have a blood flow map of the brain recorded with a positron emission tomography (PET) brain scan. A magnetic resonance imaging (MRI) scan will also be performed to determine brain anatomy. * To study the amount and distribution of dopamine receptors in the brain, participants will receive a small amount of a radioactive chemical in the vein, followed by a PET scan. * The procedure will be performed twice in two separate sessions, once for \[18F\]fallypride and once for \[11C\]NNC-112.