PET measurement of the influence of corticosteroids on serotonin-1A receptor number

Background: The hypothalamic-pituitary-adrenal (HPA) axis and serotonergic system interact functionally. The modulatory effect of corticosteroids on 5-HT1A receptor number and function has been repeatedly demonstrated in preclinical studies suggesting that raised corticosteroid levels decrease 5-HT1A receptor number and function in the hippocampus. Methods: We used positron emission tomography (PET) to quantify the number of 5-HT1A receptors in two studies, the first in normal subjects given a single dose of hydrocortisone using a random-order, double-blind, placebo-controlled design and second in patients treated long-term with corticosteroids. Results: We did not find that exposure to elevated levels of corticosteroids in either the short or long term alters 5-HT1A receptor binding in the hippocampus or other brain regions examined. Conclusions: This study does not support the hypothesis that corticosteroids exert a major inhibitory regulatory control over the 5-HT1A receptor binding in the human brain.