title: Elevated basal trough levels of corticosterone suppress hippocampal 5-hydroxytryptamine(1A) receptor expression in adrenally intact rats: implication for the pathogenesis of depression.
abstract: Several studies with adrenalectomized rats have shown that the suppressive effects of exogenous corticosteroids on 5-hydroxytryptamine(1A) receptor function are mediated by the high-affinity mineralocorticoid receptor, rather than the lower affinity glucocorticoid receptor. In the present study, adrenally intact rats were subcutaneously implanted for six days with pellets containing a small amount of corticosterone, which leads to a flattening of the circadian rhythm in the level of circulating hormone. The peak in daily corticosterone is suppressed, the basal trough is increased, and the hormone levels remain at a constant value equivalent to the daily average of about 5 microg/dl, which is usually observed in rats. Accordingly, this regime of corticosterone treatment did not enhance exclusively glucocorticoid receptor-controlled parameters, such as the weight of the thymus. Effects involving mineralocorticoid receptor activation were enhanced, since reductions were observed in stress-induced plasma corticosterone levels and adrenal weight. 5-Hydroxytryptamine(1A) receptor messenger RNA levels were found to be suppressed by approximately 25% in the dentate gyrus of the hippocampus of these corticosterone pellet-implanted rats. This suppression was reflected in significantly reduced [3H]8-hydroxy-2-(di-n-propylamino)tetralin binding in the hippocampal region. We propose therefore that this suppressive effect on 5-hydroxytryptamine(1A) receptor expression involves enhanced occupation of mineralocorticoid receptors, under a condition of elevated basal trough corticosteroid levels as is commonly observed in human depression.
authors.affiliation: Division of Medical Pharmacology, Leiden/Amsterdam Center for Drug Research, University of Leiden, The Netherlands.
authors.forename: O C
authors.initials: OC
authors.lastname: Meijer
authors.forename: R V
authors.initials: RV
authors.lastname: Van Oosten
authors.forename: E R
authors.initials: ER
authors.lastname: De Kloet
mesh_terms: D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D000311:Adrenal Glands / Q000502:physiology*; D000818:Animals; D002940:Circadian Rhythm / Q000502:physiology; D003345:Corticosterone / Q000008:administration & dosage / Q000494:pharmacology*; D003866:Depressive Disorder / Q000378:metabolism / Q000503:physiopathology*; D004343:Drug Implants; D006624:Hippocampus / Q000378:metabolism*; D008297:Male; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017208:Rats, Wistar; D011985:Receptors, Serotonin / Q000096:biosynthesis*; D017366:Serotonin Receptor Agonists
chemical_list: D004343:Drug Implants; D012333:RNA, Messenger; D011985:Receptors, Serotonin; D017366:Serotonin Receptor Agonists; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D003345:Corticosterone