Decrease in rat cerebral quinolinic acid concentration following chronic hydrocortisone treatment.

The effects of acute or repeated hydrocortisone administration were studied on the content of quinolinic acid (QUIN), 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) assessed by mass fragmentography (QUIN) and high-performance liquid chromatography (5-HT and 5-HIAA) in various brain areas of the rat. Acute administration of the steroid did not significantly modify the brain content of these tryptophan metabolites while, when repeatedly administered at doses of 5 or 50 mg/kg i.p., hydrocortisone significantly reduced the cortical content of QUIN (by 28\%, P less than 0.05 and 21\%, P less than 0.05 respectively) and the utilization of 5-HT (as evaluated from the ratio 5-HIAA/5-HT by 22\%, P less than 0.05 at 50 mg/kg). These data confirm that hydrocortisone administration affects tryptophan metabolism in the rat.