Effect of Dexamethasone on Prostaglandin Synthesis in Various Areas of the Rat Brain

Abstract: Glucocorticoid hormones are known to inhibit the production of prostaglandins in many cell types and tissues. The effect of these hormones on the biosynthesis of brain tissue is not yet clear. In the present study we investigated the effect of dexamethasone on the release of prostaglandin E₂ (PGE₂), thromboxane B₂ (TXB₂), and 6‐keto‐PGF_1α from various brain areas of male rats. Slices from cortex, hippocampus, hypothalamus, and striatum taken from rats pretreated with dexamethasone 4 mg/kg body weight or vehicle, 18 h and 2 h prior to killing, were incubated in Krebs‐Ringer‐bicarbonate for 1 h. The accumulation of PGs in the medium was determined by radioimmu‐noassay. Pretreatment with dexamethasone significantly reduced the release of all PGs from the cortex by 40–50%. In the striatum and hippocampus only TXB₂ was reduced by ∼40%. In the hypothalamus the effect of dexamethasone was not significant. When slices of the same brain areas from intactrats were incubated for 1 h in the presence of 40 μM dexamethasone, only the release of PGE₂ from the cortex was reduced (by 30%). These results suggest that glucocorticoids can inhibit PG synthesis in brain tissue, and that the cortex is the most sensitive area to the inhibitory effect of the hormone.