EXPRESSION AND SUBCELLULAR-DISTRIBUTION OF GLUTAMATE-RECEPTOR SUBUNITS-2 3 IN THE DEVELOPING CEREBELLAR CORTEX/

The expression and subcellular location of glutamate receptor subunits 2&3 was investigated in the developing postnatal cerebellum. Immunobl otting revealed that glutamate receptor subunits 2/3 is expressed in a n identical pattern of immunoreactive bands of approximately 108 kDa f rom postnatal day zero to adult animals, Light microscopy showed that within the cerebellar cortex, GluR 2/3 immunoreactivity was essentiall y confined to Purkinje neurons, Strong immunostaining could be observe d at postnatal days 1-3 within Purkinje cell bodies and primary dendri tes, With ongoing development, the cell body and an increasingly elabo rate dendritic tree was outlined by immunoreaction product. In adult a nimals, staining of Purkinje cell dendrites was patchy, and staining i ntensity of the cell body, in particular, was greatly reduced, Ultrast ructural analysis revealed that during early postnatal development, im munoreaction product was localized to the cell membrane, but was not c onfined to postsynaptic densities, From the second postnatal week, glu tamate receptor subunits 2/3 immunoreactivity was largely restricted t o postsynaptic densities, These observations reveal a developmentally regulated refinement of the subcellular distribution of defining subun its of the AMPA-type glutamate receptor, The presence of membrane boun d receptors prior to the formation of synapses also provides a rationa le for the known transmitter-mediated modulation of Purkinje cell dend ritogenesis. (C) 1996 Wiley-Liss, Inc.