Each AMPA receptor subunit was precipitated from DLPFC homogenates from normal subjects using biotinylated lectins to isolate glycosylated proteins. Proteins that bound to lectins were separated by SDS–polyacrylamide electrophoresis, transferred to nitrocellulose membranes, and probed using specific antisera for each AMPA receptor subunit. Representative immunoblots show that most lectin binding was associated with the GluR2 and GluR4 subunits. Abbreviations: C, tissue homogenate. PNA, ConA, NPL, HHL, LEL are lectins as described in Table 2.