DEVELOPMENTAL-CHANGES IN EXPRESSION AND DISTRIBUTION OF THE GLUTAMATE-RECEPTOR CHANNEL DELTA-2 SUBUNIT ACCORDING TO THE PURKINJE-CELL MATURATION

The glutamate receptor (GluR) channel delta 2 subunit is considered to be a functional molecule involved in motor coordination, Purkinje cel l synapse formation and cerebellar long-term depression. We examined d evelopmental changes in expression and distribution of the GluR delta 2 in the mouse cerebellum by in situ hybridization and immunohistochem istry. The GluR delta 2 mRNA was detected as early as embryonic day 15 (E15) in a cell mass consisting of Purkinje neuroblasts in the poster ior cerebellum. During late embryonic and postnatal periods, the GluR delta 2 mRNA was expressed abundantly and specifically in Purkinje cel ls. By immunohistochemistry, immunoreactivity of the GluR delta 2 was found in both shafts and spines of Purkinje dendrites at early postnat al period. By P21, however, the intense immunoreactivity became restri cted to the dendritic spines, especially along the postsynaptic membra ne in contact with parallel fiber terminals. These findings suggested that the transcription of the GluR delta 2 subunit occurs in the Purki nje cells from fetal through adult stage, but the intracellular locali zation of the protein products undergoes an alteration from non-synapt ic to synaptic site when active synaptogenesis takes place.