[MS6-3B-3] Developmental change of GABAergic system measured with 123I-iomazenil SPECT
[Objective] 123I-iomazenil (IMZ) is a specific ligand of central benzodiazepine receptor (BZR) which is a part of the postsynaptic GABA-A receptor complex. We performed retrospectively statistical image processing to evaluate maturational change of GABAergic system. This study was approved by the ethics committee of Saitama Children’s Medical Center. [Method] The subjects were 30 patients (aged 17days to 14years) with cryptogenic localization-related epilepsy. They met the following criteria: (1) no visible abnormalities in IMZ-SPECT distribution; (2) no neurological abnormalities without epilepsy and no developmental delay; (3) not taking benzodiazepine medication. A triple-head gamma camera scanned 3 hours after injection. We used semiquantitative analytical method which is consist of brain surface extraction and anatomical normalization. The RI counts in each brain area plotted in age order. [Result] All brain regions showed the highest BZR binding activity in infantile period and it has largely decreased by the age of 2. The distribution of IMZ in primary sensorimotor cortex, cerebellar vermis, striatum and occipital cortex declined earlier than that of cerebellar hemisphere and frontal cortex did. [Conclusion] The exponential decrease of BZR binding activity in infancy may reflect synaptic pruning and GABA-A receptor subunit expression. Maturational change of BZR binding activities has started from phylogenetically primitive brain regions. Maturational change of GABAergic system in cerebral cortex was similar to the pattern of myelination.