Age-related decreases in corticotropin-releasing factor (CRF) receptors in rat brain and anterior pituitary gland

Corticotropin-releasing factor (CRF) receptors were measured in discrete areas of brain and in anterior pituitary of 4-, 12-, 18-, and 24-month-old male Fischer rats. No significant age-related alterations in [ 125I]ovine CRF binding were observed in the olfactory bulb, cerebral cortex, hippocampus, brainstem, and cerebellum; there was a trend for CRF binding to decrease in the striatum as a consequence of aging. Significant age-related decreases were observed in 125I-ovine CRF binding in the anterior pituitary and hypothalamus with maximal reductions of 60 and 27%, respectively. Saturation analysis in the anterior pituitary indicated an age-related reduction in the density of CRF receptors (i.e. B max) without an alteration in the affinity (i.e. K d) of CRF for its binding site. Northern analysis of proopiomelanocortin (POMC) mRNA in the anterior pituitary indicated no significant differences in the levels of POMC mRNA between 4- and 24-month-old rats. These and other data suggest that the age-related decrease in anterior pituitary CRF receptors may be due to hypersecretion of hypothalamic CRF rather than a l a loss of corticotropes in the anterior pituitary.