Effects of corticosterone on 5-HT(1A) and 5-HT₂ receptor binding and on the receptor-mediated behavioral responses of rats

The effects of corticosterone after binding to 5-HT(1A) and 5-HT₂ receptors were studied in rats. Binding of [³H]8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT) to 5-HT(1A) receptors in the hippocampus decreased 24 h after both acute and chronic (14 day) administration of CORT (50 mg/kg, s.c.). Chronic, but not acute, CORT treatment increased [³H]ketanserin binding to 5-HT₂ receptors in the frontal cortex. Receptor-mediated behavioral responses were also examined following acute and chronic CORT treatment. Flat body posture and hypothermia induced by 8-OH-DPAT, a 5-HT(1A) receptor agonist, were attenuated following chronic, but not acute, CORT administration. (±)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI), a 5-HT₂ receptor agonist, induced wet-dog shakes, but not hyperthermia and this response was increased 24 h after the chronic administration of CORT, These findings indicate that both 5-HT(1A) and 5-HT₂ receptor functions were changed following chronic exposure to high levels of CORT. Such changes in these receptor systems may play an important role in the etiology of affective disorders.