Brain radioligands - State of the art and new trends

Non-invasive radioligand imaging methods for brain receptor studies use eit her short-lived positron-emitting radionuclides such as C-11 and F-18 for p ositron emission tomography (PET) or single photon-emitting radionuclides s uch as I-123 for single photon emission computed tomography (SPECT). PET an d SPECT use radioligands which are injected intravenously into experimental animals, human volunteers or patients. The main applications of radioligan ds in brain research concern human neuropsychopharmacology and the discover y and development of novel drugs to be used in the therapy of neurological and psychiatric disorders. A basic problem in PET and SPECT brain receptor studies is the lack of useful radioligands with appropriate binding charact eristics. Prerequisite criteria need to be satisfied for a radioligand to r eveal target binding sites in vivo. This section will discuss these importa nt criteria and also review recent examples in neuroreceptor radioligand de velopment such as selective radioligands for brain monoamine transporters.