Sleep Regulates Incubation of Cocaine Craving

After withdrawal from cocaine, chronic cocaine users often experience persistent reduction in total sleep time, which is accompanied by increased sleep fragmentation resembling chronic insomnia. This and other sleep abnormalities have long been speculated to foster relapse and further drug addiction, but direct evidence is lacking. Here, we report that after prolonged withdrawal from cocaine self-administration, rats exhibited persistent reduction in nonrapid-eye-movement(NREM) and rapid-eye-movement(REM) sleep, as well as increased sleep fragmentation. In an attempt to improve sleep after cocaine withdrawal, we applied chronic sleep restriction to the rats during their active (dark) phase of the day, which selectively decreased the fragmentation of REM sleep during their inactive (light) phase without changing NREM or the total amount of daily sleep. Animals with improved REM sleep exhibited decreased incubation of cocaine craving, a phenomenon depicting the progressive intensification of cocaine seeking after withdrawal. In contrast, experimentally increasing sleep fragmentation after cocaine self-administration expedited the development of incubation of cocaine craving. Incubation of cocaine craving is partially mediated by progressive accumulation of calcium-permeable AMPA receptors (CP-AMPARs) in the nucleus accumbens (NAc). After withdrawal from cocaine, animals with improved REM sleep exhibited reduced accumulation of CP-AMPARs in the NAc, whereas increasing sleep fragmentation accelerated NAc CP-AMPAR accumulation. These results reveal a potential molecular substrate that can be engaged by sleep to regulate cocaine craving and relapse, and demonstrate sleep-based therapeutic opportunities for cocaine addiction.