MAP2B, NR1, PSD-95, and SAP102 are unchanged in old rats. Hippocampal samples were homogenized in 1% Triton X-100 (A) or 1% deoxycholate (B), and soluble and insoluble proteins were separated by ultracentrifugation. (A) Aliquots of comparable amounts of supernatants (Right) and pellets (Left) were analyzed by immunoblotting with antibodies against MAP2B and NR1 and quantified by densitometry. (B) Aliquots of the supernatants were analyzed either directly by immunoblotting with anti-PSD-95 and anti-SAP102 (Left) or after their coprecipitation with NMDA receptors by using a mixture of anti-NR2A and NR2B antibodies for immunoprecipitation (Right). All values were normalized with respect to the average values for each set of markers from adult rats, which corresponded to 100%. Bars represent average of n samples ± SEM (n is given in each bar).