Abstract
1. Prostaglandin-like material has been found in superfusates of cerebral cortex in unanaesthetized encéphale isolé cat preparations.2. The material was assayed on the isolated rat uterus and identified by thin-layer chromatography.3. The level of spontaneous release of prostaglandin-like material was greater than that which had been found in anaesthetized preparations and it increased further with electrical stimulation of the reticular formation which induced electrocortical arousal.4. Chlorpromazine (1.0-8.0 mg/kg) not only depressed the spontaneous release but blocked the increase evoked by stimulation concomitantly with blocking electrocortical arousal. Increasing the stimulating voltage to restore the arousal response also restored the evoked release of prostaglandins.5. Most of the prostaglandin-like material released spontaneously was represented by E type compounds, but the increase with stimulation was mainly of F compounds.