Mice were perfused with 0.1M PBS and 4% paraformaldehyde and brains were post-fixed for 24 h. For dendritic spine morphology and virus placement, 100 μm sections were blocked in 3% normal donkey serum and 0.3% Triton X-100 in PBS for 30 min, then incubated in chicken anti-mCherry (1:500; Novus Biologicals, NBP2 25158) and in rabbit anti-GFP (1:500; Cell Signaling #2555) overnight at 4°C as in 34 (link), 35 (link). For virus validation a mouse monoclonal anti-Nr4a1 antibody (1:1000; #sc-365113, Santa Cruz) or a polyclonal rabbit anti-SaCas9 (1:1000; #ab203933, Abcam) were used. Following eight 1 h-PBS washes slices were incubated overnight in anti-chicken-Cy3 (1:1000, Jackson Immuno; #703–165-155) and anti-rabbit-Alexa 488 (1:1000, Jackson Immuno; #111–545-003) or anti-mouse Cy2 (1:1000, Jackson Immuno; #715–225-150), anti-rabbit Cy5 (1:1000, Jackson Immuno; #711–175-152) depending on the condition at 4°C. Finally, following eight 1 h-PBS washes, slices were mounted with Aqua-Poly/Mount (Polysciences) mounting media.