Prostaglandin E1 causes sedation and increases 5-hydroxytryptamine turnover in rat brain

1. Administration of prostaglandin E(1) (1 mg/kg, i.p.) to rats induced sedation and a decrease in muscular tone. Prostaglandin E(1)-induced sedation was accompanied by the low voltage-high frequency E.E.G. pattern characteristic of the waking animal.2. Administration of prostaglandin E(1) also increased the turnover rate of 5-hydroxytryptamine and raised the concentration of acetylcholine in brain.3. The behavioural effects of prostaglandin were blocked by prior administration of p-chlorophenylalanine or pargyline, drugs which lowered the brain concentration of 5-hydroxyindoleacetic acid (5-HIAA), and was potentiated by pretreatment with probenecid, which elevated the 5-HIAA concentration. Pretreatment with atropine sulphate failed to alter prostaglandin E(1)-induced sedation.4. The results are compatible with the possibility that prostaglandin E(1) induces a state resembling paradoxical sleep through an action on 5-hydroxytryptamine metabolism in brain.