Impaired up-regulation of type II corticosteroid receptors in hippocampus of aged rats

J. Charles Eldridge, Deidre G. Fleenor, D. Steven Kerr, Philip W. Landfield

Research output: Contribution to journalArticlepeer-review

61 Scopus citations

Abstract

Several recent investigations have reported a decline of rat hippocampal corticosteroid-binding receptors (CSRs) with aging. This decline has been proposed to be an initial cause (through disinhibition) of the elevated adrenal steroid secretion that apparently occurs with aging; however, it could instead be an effect of corticoid elevation (through down-regulation). In order to assess the effects of age on CSR biosynthetic capacity in the absence of down-regulatory influences of endogenous corticoids, as well as to study aging changes in CSR plasticity, we examined the up-regulation of hippocampal CSR that follows adrenalectomy (ADX). The rat hippocampus contains at least two types of CSR binding and differential analysis of types I and II CSR was accomplished by selective displacement of [3H]corticosterone with RU-28362, a specific type II agonist. In young (3 months old) Fischer-344 rat hippocampus, up-regulation of type II binding above 2-day ADX baseline was present by 3-7 days and increased still further by 8-10 days post-ADX; type I CSR density did not change significantly between 1 and 10 days post-ADX. However, in aged (24-26 months old) rats, type II CSR up-regulation did not occur over the 10 day post-ADX period. Thus, the age-related impairment of type II up-regulation may reflect an intrinsic deficit in CSR biosynthesis or lability that is independent of the acute endogenous adrenal steroid environment.

Original languageEnglish
Pages (from-to)248-256
Number of pages9
JournalBrain Research
Volume478
Issue number2
DOIs
StatePublished - Jan 30 1989

Keywords

  • Adrenalectomy
  • Aging
  • Corticosteroid receptor
  • Corticosterone
  • Hippocampus
  • Up-regulation

ASJC Scopus subject areas

  • General Neuroscience
  • Molecular Biology
  • Clinical Neurology
  • Developmental Biology

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