(A) Left, Western blot image showing newly synthesized proteins labeled with puromycin using the SUnSET technique (see Experimental Procedures). Coronal prefrontal slices from wild-type and PERK cKO mice were treated with puromycin (5µg/mL) for 45 mins. Right, Protein synthesis levels remain unaltered between both genotypes. (cntl, no puromycin control, n=4; WT, n=4; cKO, n=4). (B) Absorbance profile (254 nm) of WT (black trace) and PERK cKO (red trace) prefrontal cortical fractions sedimented through a 20–50% linear sucrose gradient in the presence of cycloheximide.