GABA Receptor Imaging / 핵의학분자영상

ABSTRACT

GABA is primary an inhibitory neurotransmitter that is localized in inhibitory interneurons. GABA is released from presynaptic terminals and functions by binding to GABA receptors. There are two types of GABA receptors, GABAA-receptor that allows chloride to pass through a ligand gated ion channel and GABAB-receptor that uses G-proteins for signaling. The GABAA-receptor has a GABA binding site as well as a benzodiazepine binding sites, which modulate GABAA-receptor function. Benzodiazepine GABAA receptor imaging can be accomplished by radiolabeling derivates that activates benzodiazepine binding sites. There has been much research on flumazenil (FMZ) labeled with 11C-FMZ, a benzodiazepine derivate that is a selective, reversible antagonist to GABAA receptors. Recently, 18F-fluoroflumazenil (FFMZ) has been developed to overcome 11C's short half-life. 18F-FFMZ shows high selective affinity and good pharmacodynamics, and is a promising PET agent with better central benzodiazepine receptor imaging capabilities. In an epileptic focus, because the GABA/benzodiazepine receptor amount is decreased, using 11C-FMZ PET instead of 18F-FDG PET, restrict the foci better and may also help find lesions better than high resolution MR. GABAA receptors are widely distributed in the cerebral cortex, and can be used as an viable neuronal marker. Therefore it can be used as a neuronal cell viability marker in cerebral ischemia. Also, GABA-receptors decrease in areas where neuronal plasticity develops, therefore, GABA imaging can be used to evaluate plasticity. Besides these usages, GABA receptors are related with psychological diseases, especially depression and schizophrenia as well as cerebral palsy, a motor-related disorder, so further in-depth studies are needed for these areas.