Abstract:

Stereoselective competition was used to determine (3H)-aldosterone binding to type I corticosteroid receptors, and (3H)-dexamethasone binding to type II receptors in punches obtained from 11 brain regions of short-term adrenalectomized (ADX) rats. It was observed that type I receptor binding was almost exclusive of the hippocampus (HIPPO), while type II receptor binding was more generally distributed among HIPPO, cerebral cortex, lateral septum, ventromedial and arcuate hypothalamic nuclei, with lower levels in 6 additional regions studied. We determined corticosterone (CORT) in brain punches from ADX rats, ADX rats receiving CORT for 5 days, intact rats and intact rats receiving ACTH for 5 days. We correlated (3H)-ligand binding with CORT content in punches obtained from identical brain regions and showed a significant positive correlation in the case of the ADX plus CORT group, for type II corticosteroid receptors. Similarly, a significant correlation emerged with type II sites, when binding capacity was correlated with percentage increases of CORT in brain areas of rats receiving ACTH. It is suggested that in situations where CORT levels are elevated, changes in CORT retention throughout the brain occur as a function of the type II glucocorticoid receptor, although at the level of the HIPPO, both receptors may provide appropriate control of the CNS-pituitary-adrenal axis, according to the physiological or stress levels of circulating hormone.