Corticosteroids regulate 5-HT1A but not 5-HT1B receptor mRNA in rat hippocampus

The role of mineralocorticoid and glucocorticoid receptors (MR and GR, respectively) in the regulation of serotonin receptors has not been clearly delineated. There is no consensus regarding the regulation of 5-HT1A receptors, and corticosteroid regulation of 5-HT1B mRNA has not been previously studied. We compared the effects of long-term (two week) adrenalectomy (no MR or GR activation) and several hormone replacement protocols designed to stimulate MR selectively (ALDO), MR and GR (HCT), and continuous MR with cyclical GR activation (SHAM adrenalectomy). 5-HT1A and 5-HT1B mRNAs were measured by in situ hybridization in hippocampus and raphe nuclei. None of the experimental manipulations altered 5-HT1B mRNA levels in the hippocampus or dorsal raphe, and also had no effect on 5-HT1A mRNA in dorsal or median raphe. However, 5-HT1A mRNA levels were regulated in a complex manner in the different subfields of hippocampus. We conclude that both MR and GR play an integrated role in regulating 5-HT1A mRNA levels in hippocampus while having no effect on 5-HT1B mRNA levels under these conditions.