Regulation of phosphorylation of synaptic and extrasynaptic GluA1 AMPA receptors in the rat forebrain by amphetamine

The AMPA receptor is regulated by phosphorylation. Two major phosphorylation sites (5831 and 5845) are located in the intracellular C-terminal tail of GluA1 subunits. The phosphorylation on these sites controls receptor expression and function and is subject to the regulation by psychostimulants. In this study, we further characterized the regulation of 5831 and 5845 phosphorylation by amphetamine (AMPH) in the adult rat striatum and medial prefrontal cortex (mPFC) in vivo. We focused on the specific fraction of GluA1/AMPA receptors enriched from synaptic and extrasynaptic membranes, using a pre-validated biochemical fractionation procedure. We found that acute AMPH administration elevated GluA1 5845 phosphorylation in the defined synaptic membrane born the striatum in a dose-dependent manner. AMPH also induced a comparable increase in 5845 phosphorylation in the extrasynaptic fraction of striatal GluA1. Similar increases in 5845 phosphorylation in both synaptic and extrasynaptic pools were observed in the mPFC. In contrast, 5831 phosphorylation was not altered in synaptic and extrasynaptic GluA1 in striatal neurons and synaptic GluA1 in mPFC neurons in response to AMPH, although a moderate increase in 5831 phosphorylation was seen in extrasynaptic GluA1 in the mPFC after an AMPH injection at a high dose. Total synaptic and extrasynaptic GluA1 expression remained stable in the two regions after AMPH administration. Our data demonstrate the differential sensitivity of 5845 and 5831 phosphorylation to dopamine stimulation. 5845 is a primary site where phosphorylation of GluA1 is upregulated by AMPH in striatal and mPFC neurons at both synaptic and extrasynaptic compartments. (C) 2013 Elsevier B.V. All rights reserved.