Sleep is a universal state, typically preceded by preparatory routines such as grooming, nest-building, and locating a sleeping spot. These behaviors are essential for sleep consolidation, and their disruption, particularly by negative emotions, may alter sleep quality. To investigate the interaction between emotional regulation and sleep, we employed a rodent model of frustration, the consummatory Successive Negative Contrast (cSNC) paradigm, in which the unexpected devaluation of a reward induces emotional dysregulation. We combined this paradigm with pre-sleep behavioral video analysis and electroencephalographic/electromyographic monitoring. We observed that after the reward devaluation, downshifted animals displayed an initial increase in locomotion, followed by fewer REM sleep episodes during the light phase, delayed sleep-onset and poorer nest quality. In a second experiment, we repeated the protocol but added a 6h sleep deprivation manipulation after sucrose exposure on the last 4 days pre-shift. Preliminary data showed that both deprived and undisturbed downshifted animals further delayed their sleep-onset and decreased their rest time following reward devaluation. These findings suggest that frustration disrupts sleep architecture and that these alterations are aggravated by previous sleep debt. Key Words: Emotional frustration, Sleep/wake cycle, Pre-sleep, Frustration and sleep, Consummatory Successive Negative Contrast, Sleep Deprivation