Rapid eye movement sleep deprivation disrupts context-modulated effects on morphine locomotor sensitization in mice

Previous studies have shown that behavioral sensitization is modulated by drug-associated context, in which memory processes may be critically involved. Sleep has been suggested to play an important role in memory processes. However, the relationship between sleep and context-modulated effects on behavioral sensitization remains to be elucidated. In the present study, we designed three experiments to explore the effects of rapid eye movement sleep deprivation (RSD) on context-modulated effects on morphine locomotor sensitization in mice. Mice were subjected to 6h RSD starting either immediately after morphine pairing training or 6h later. The control mice were returned to their home cages immediately after pairing training and left undisturbed. In experiment 1, RSD from 0 to 6h but not from 7 to 12h disrupted paired context-modulated enhancement of locomotor activity. In experiment 2, RSD from 0 to 6h but not from 7 to 12h disrupted unpaired context-modulated suppression of locomotor activity. In experiment 3, RSD from either 0 to 6h or 7 to 12h had no effect on conditioned locomotor activity. Our findings suggest that sleep plays a critical role in memory processes underlying context-modulated effects on morphine locomotor sensitization.