Mice were deeply anesthetized and transcardially perfused with 0.1 M phosphate-buffered saline (PBS) followed by 4% paraformaldehyde in PBS. After removal, brains stayed overnight in 4% paraformaldehyde. For cryoprotection, brains were stored in 30% sucrose (w/v) in PBS solution for at least 1 night. Brains were sliced in 30 or 40 μm sections using a
cryostat (Leica). For immunohistochemistry, non-specific binding sites were blocked by incubating the brain sections in 2%
goat serum (Millipore) in PBST (0.3% Triton X-100 in PBS).
To amplify the fluorescence of axon fibers expressing ChR2-eYFP or eYFP, we applied antibodies for GFP (
A11122, Life Technologies, 1:1000). Brain sections were incubated with the primary antibody diluted in blocking solution for 2 nights. A species-specific secondary antibody conjugated with green Alexa fluorophore (
A11008, Life Technologies, 1:1000; goat anti-rabbit) was diluted in PBS and applied for 2 h. Fluorescence images were taken using a confocal microscope (
LSM 710 AxioObserver Inverted 34-Channel Confocal, Zeiss), fluorescence microscope (Keyence, BZ-X710), and
Nanozoomer 2.0 RS (Hamamatsu).
Weber F., Hoang Do J.P., Chung S., Beier K.T., Bikov M., Saffari Doost M, & Dan Y. (2018). Regulation of REM and Non-REM Sleep by Periaqueductal GABAergic Neurons. Nature Communications, 9, 354.