Induction of serine racemase by Aβ. Serine racemase protein was detected by western blot analysis of lysates of primary microglia. A. Microglial proteins were probed with antibody that either had (+) or had not (-) been preabsorbed to recombinant serine racemase. The detection was intentionally overdeveloped to demonstrate nonspecific bands distinct from the monomer and unreducible dimer. B. Microglia were incubated in triplicate for 12 h either with (+) or without (-) 15 μM Aβ1–42. Arrowhead designates monomer and arrow dimer. Results are representative of three experiments. Densitometry of the dimer in digitized images indicated a significant difference between treated and untreated samples [cntrl: 139.97 ± 54.92, Aβ: 418.52 ± 74.37 (arbitrary units); p < 0.02, unpaired Student's t-test].