Western blot of rat cortex lysate showing specific immunolabeling of the ~78k synapsin I phosphorylated at Ser9 (Control). The phosphospecificity of this labeling is shown in the second lane (lambda-phosphatase: I>>-Ptase). The blot is identical to the control except that it was incubated in I>>-Ptase (1200 units for 30 min) before being exposed to the phospho-Ser9 synapsin I antibody. The immunolabeling is completely eliminated by treatment with I>>-Ptase.