Fig. 1. Sleep/wake state across a 24 h period is organized into recurring bouts during which sleep primarily occurs during the light phase and wakefulness during the dark phase.

A Rats were implanted with EEG/EMG electrodes. After 7 days of recovery, rats were acclimated to recording chambers for 16 h prior to recording of sleep/wake activity for 24 h. Following sleep recordings, rats were sacrificed 6 h into the light phase (ZT6) or 6 h into the dark-phase (ZT18) and brains were prepared for FSCV recordings in the NAc core. A separate group of rats was subjected to the same sleep recording procedures except that after sacrifice, the NAc was dissected for western blot analysis of plasma membrane fractions of DAT and phosphorylated DAT. B Representative EEG and EMG recordings. C Example hypnogram across a 24 h period. White bar represents the light phase and the black bar represents the dark phase. D Mean percentage of time rats spent in Wake, NREM, and REM during the light and dark phase for the full 24 h recording (n = 18 rats).