Paradoxical sleep and memory: Long-term disruptive effects of anisomycin

The effects of the protein synthesis inhibitor Anisomycin (ANI) on Paradoxical Sleep (PS or REM sleep), slow wave sleep (SWS), and retention of one-trial inhibitory avoidance training was examined in mice in three separate experiments. In Experiment 1, mice injected with ANI 120 mg/kg and 210 mg/kg exhibited reductions in PS for 9 consecutive hours and ANI 40 mg/kg treated mice for 6 consecutive hours with no PS rebound in all three groups. ANI increased SWS commencing 3 hr postinjection, continuing for 9 consecutive hours and then returning to saline control levels. There were no significant differences between ANI-treated groups in the degree of SWS augmentation. In Experiment 2, Part A, ANI 120 mg/kg and 210 mg/kg but not ANI 40 mg/kg impaired retention measured 72 hr after training. In Experiment 2, Part B, ANI 120 mg/kg and 210 mg/kg induced amnesia from 3 to 9 hr post-training but ANI 40 mg/kg was effective only from 3 to 6 hr. In Experiment 3, the gradient of memory trace susceptibility to disruption by ECS was extended to 3 hr post-training in mice given immediate post-training injections of ANI 40 mg/kg. ANI 20 mg/kg and ANI 10 mg/kg alone or in combination with ECS was ineffective in extending the lability of the memory trace. The results of this study indicate that PS in the 3 hr period after aversively motivated training is not essential for memory processing. We suggest that memory stability and maintenance is dependent on PS occurring over a protracted time period.