Optogenetic Modulation of Sleep-Wake Cycles

Before stimulation, the fiber optic cannulas were connected with a 473 nm blue laser or 589 nm yellow laser diode^{49 (link),56 (link)}. Light pulse trains were generated by a stimulator (SEN-7103, Nihon Kohden, Japan) and output by an isolator (ss-102J, Nihon Kohden). For instantaneous photostimulation, each trial was applied 20 s after a stable NREM or REM sleep event by observing the online EEG/EMG display. For prolonged photostimulation, programmed light pulse trains (5 ms pulses at 20 Hz for 30 s and at 30 s intervals for 1 h) were used from 9:00 to 10:00. The recorded EEG/EMG during the same period of PSTN-mCherry mice served as the control. Animals were perfused after receiving 1 h-prolonged photostimulation for c-Fos staining. The light intensity at the tip of the optical fiber was tested by a power meter (PM10, Coherent) before each experiment time and calibrated to emit 20–30 mW/mm². For the open-field test, programmed light pulse trains (5 ms pulses at 20 Hz for 30 s and at 30 s intervals for 10 min) were used after the mice had adapted to the field environment for 5 min.