Microdialysis and EEG in rats reveal cortical PGE2 changes during sleep and wakefulness

Prostaglandin (PG) E2 production was assessed in freely moving rats using the technique of microdialysis in the prefrontal cortex associated with parallel cortical EEG recordings. PGE2 concentrations were 40% higher during wakefulness than during slow wave sleep. PGE2 values varied during wakefulness with a maximal increase in the middle of the stage and a drop towards lower values before the occurrence of slow wave sleep. These variations were similar to those observed previously in the rostromedial hypothalamus, where PGE2 concentration was 2.6 times lower than that in the cortex. These data document a positive correlation between cortical EEG activation and PGE2 levels. Taken together with pharmacological data on the awakening effect of centrally administered PGE2, these observations are in favor of an involvement of PGE2 in the generation of wakefulness.