Western blot of rat hippocampal lysate showing specific immunolabeling of the ~100k GluR1 protein phosphorylated at Ser831 (Control). The phosphospecificity of this labeling is shown in the second lane (lambda-phosphatase: ?-Ptase). The blot is identical to the control except that it was incubated in ?-Ptase (1200 units for 30 min) before being exposed to the GluR1 Ser831 antibody. The immunolabeling is completely eliminated by treatment with ?-Ptase.