 By adulthood, the level of expression in the cerebral cortex and hippocampus drops below developmental expression levels, but the expression in the cerebellum does not change postnatally.The highest levels of Gabrb3 expression in the mature mouse brain occur in the Purkinje and granule cells of the cerebellum, the hippocampus, and the piriform cortex.In humans, the beta-3 subunit, as well as the subunits of its two neighbouring genes (GABRG3 and GABRA5), are bi-allelically expressed within the cerebral cortex, indicating that the gene is not subjected to imprinting within those cells.