Autoradiographic analyses of the effects of adrenalectomy and corticosterone on 5-HT1A and 5-HT1B receptors in the dorsal hippocampus and cortex of the rat.

Quantitative autoradiography was used to evaluate the effects of adrenalectomy (ADX) and corticosterone (CORT) on binding at 5-HT1A and 5-HT1B receptors in the dorsal hippocampus and cortex of the rat. ADX increased binding of [3H]8-hydroxy-2-(di-n-propylamino)tetralin at 5-HT1A receptors in the oriens and lacunosum moleculare layers of CA2 and CA3, in the lacunosum moleculare layer of CA4 region, and in the dentate gyrus. In restraint-stressed ADX rats, binding was increased only in the oriens and lacunosum moleculare layers of CA2. Restoration of baseline levels of CORT reversed the effects of ADX on 5-HT1A receptors in the hippocampus, while high levels of CORT decreased binding at 5-HT1A receptors in the dentate gyrus. No treatment affected binding at 5-HT1A receptors in the CA1 region of the hippocampus or in the cortex. ADX increased binding of [125I]iodocyanopindolol at 5-HT1B receptors in the infrapyramidal dentate, but this effect was not observed in ADX rats that were restrained. CORT treatment in both ADX and SHAM (adrenally intact) rats resulted in binding at 5-HT1B receptors that was lower than that in untreated ADX and SHAM rats in the infrapyramidal dentate, and lower than that in ADX rats in the suprapyramidal dentate and CA4. In ADX and SHAM rats, CORT also reduced binding at 5-HT1B receptors in area 2 of the cortex. It is suggested that decreases in binding at 5-HT1A and 5-HT1B/1D receptors resulting from chronic exposure to high levels of CORT may also occur in animals that fail to adapt to chronic severe stress. Such changes in binding may play important roles in the etiology of depression.