AMPA receptor development in rat telencephalon: [3H]AMPA binding and western blot studies

Telencephalic membranes from rats of different embryonic (E16, E19) and postnatal (P2, P7, P14, adult) ages were assessed for alpha-[3H]amino-3-hydroxy-5-methylisoxazole-4-propionic acid ([3H] AMPA) binding and for immunoreactivity levels of AMPA receptor subunits (GluR1, GluR2/3, and GluR4). In addition, the synaptic markers synaptophysin and NCAM140 (a neural cell adhesion molecule isoform) were examined by immunoblot. The density of [3H]AMPA binding sites increased steadily with advancing age. This increase was due mainly to the development of the large low-affinity component (KD = 400 nM) that dominates the [3H]AMPA binding profile of adult rat brain membranes. As resolved by two-site regression analysis, the high-affinity component (KD = 15 nM) of the [3H]AMPA binding increased by approximately twofold from E16 to adult, whereas the low-affinity component increased by 25-fold. Staining for GluR1 and GluR2/3 increased steadily with increasing age at all time points examined; synaptophysin and NCAM140 exhibited similar ontogenic immunostaining profiles. GluR4 immunoreactivity was first evident at P14 and increased by adulthood.(ABSTRACT TRUNCATED AT 250 WORDS)