Maturational Changes in the Subunit Composition of AMPA Receptors and the Functional Consequences of Their Activation in Chicken Forebrain

AMPA receptors play a critical role in synaptic plasticity and brain development. Here we show that Ca 2+ uptake in response to AMPA receptor activation decreases dramatically during maturation in chicken brain microslices without a change in tissue AMPA receptor content. We found that during maturation the relative concentration of GluR2 subunits increased, the concentration of the AMPA receptor-associated scaffold proteins SAP97 and GRIP decreased and that depolarization increased GluR1 phosphorylation at Ser831 in subcellular fractions enriched in postsynaptic densities at 2 weeks but not at 10 weeks. These changes are all consistent with a decreased Ca 2+ entry through AMPA receptor channels in response to receptor activation and may account for the changes in the functional properties of the receptor, which are thought to underlie, at least in part, the physiological changes that occur with maturation.