Brain Glucocorticoid Receptor Research Articles

Ontogeny of the Type 2 glucocorticoid receptor in discrete rat brain regions: an immunocytochemical study

The ontogeny of the Type 2 glucocorticoid receptor (GR) in the rat brain was examined using a monoclonal antibody raised against the rat liver GR. Marked changes both in the intensity and in the localization of GR immunoreactivity (GR—ir) were found to occur as a function of age and brain area examined. First, GR-ir was high perinatally and decreased to a low intensity of immunostaining around postnatal day 12 (pnd 12). Thereafter, GR-ir increased to a moderate intensity, which resembled adult levels by pnd 20 in most brain areas. Second, in some regions, such as the hippocampal CA3-4 pyramidal cell fields and the suprachiasmatic nucleus of the hypothalamus, GR-ir was only clearly present during the first postnatal week. Third, in the hippocampus, GR-ir localization showed a distinctive developmental trend towards greater compactness within the CA1-2 pyramidal cell fields and a greater restriction of immunoreactive staining to these cell fields with exclusion of the adjoining areas. Fourth, adrenalectomy reduced overall GR-immunopositive staining, which could be reversed by administration of the selective glucocorticoid agonist, RU 28362. Our results suggest that during ontogeny the glucocorticoid receptor system displays considerable plasticity. Such plasticity may provide a basis for understanding the role of glucocorticoids during brain development.

Immunocytochemical study on the intracellular localization of the type 2 glucocorticoid receptor in the rat brain

The localization of the glucocorticoid receptor (GR) (type 2) in the rat brain was studied with immunocytochemistry using a monoclonal antibody against the rat liver GR. Strong GR immunoreactivity (GR-ir) was observed in neurons of limbic and brainstem structures known to be associated with the stress-activated circuitry, which suggest that these sites are responsive to glucocorticoid feedback. The intracellular localization of GR-ir was examined in CA 1 and CA 2 pyramidal neurons of the hippocampus. In intact rats GR-ir is predominantly present in the cell nucleus. Adrenalectomy (ADX) caused a slow depletion of the GR-ir signal from the cell nucleus until near detection limits at two weeks postsurgery. At that time, 1 h after administration to longterm ADX rats the synthetic glucocorticoid (type 2) agonist RU 28362 as well as a moderate and high dose of corticosterone (CORT) markedly enhanced the cell nuclear Gr-ir. The type 2 antagonist RU 38486 also caused an increase of GR immunostaining in cell nuclei upon acute administration to ADX rats. The mineralocorticoid aldosterone (ALDO) and a low dose of CORT, which bind almost exclusively to type 1 corticosteroid receptors, were ineffective. In conclusion, our data suggest that in the hippocampal Ca 1–2 neurons type 1 and type 2 corticosteroid receptors may coexist. The steroid-induced changes in cell nuclear immunoreactive GR staining intensity suggest possible cytoplasmic-cell nuclear translocation of GR and/or exposure of immunogenic GR domains.

Photoaffinity labeling with [ 3H]RU 28362: A powerful tool for the study of rat brain glucocorticoid receptors

In order to study the receptor system for adrenocortical steroids in rat brain the synthetic glucocorticoid RU 28362 (11β,17 β-dihydroxy-6-methyl-17 α-(1-propynyl) androsta-1,4,6-trien-3-one) has been used for photoaffinity labeling. Competition and dissociation studies revealed a single class of binding sites for RU 28362 in rat brain cytosol. Photoaffinity labeling was performed by u.v.-irradiation for 2 min with a coupling efficiency of about 25%. The high efficiency permitted investigation of crude cytosolic preparations under denaturating conditions. Sodium dodecyl sulfate (SDS) and high resolution two-dimensional gel electrophoresis confirmed the high specificity of the photoaffinity labeling. The molecular weight (93 kD) as well as the isoelectric point (5.6) evaluated by these methods corresponded well to data reported for the classical glucocorticoid receptor in rat liver.

Cholinesterase activities in blood in infantile autism

of Functional Disorders (ed 3). New York: New York State Psychiatric Institute. Tome110 S, Orth E, De Nicola AF, Rainbow TC, McEwen BS (1982): Regulation of glucocorticoid receptor in brain by corticosterone treatment of adrenalectomized rats, Neuroendocritwlogy 35:411. Vale W, Spiess J, Rivier C, Rivier J (1981): Characterization of a 41-residue ovine hypothalamic peptide that stimulates secretion of corticotropin and B-endorphin. Science 213:1341-1397. World Health Organization (1980): Degkwitz R, Helmchen H, Kockott G, Mombour W (eds), Mental Disorders: Glossary and Guide to Their Classijcation in Accordance with the Ninth Revision of the International Classification of Diseases. New York: Springer.

Cortisol 17β acid, transcortin, and the heterogeneity of rat brain glucocorticoid receptors

Binding of tracer or competing steroids to transcortin can compromise specificity studies on receptors for adrenal steroids. Recently Alexis et al.[l] have used Cortisol 17β acid at high concentrations to prevent steroid binding to any transcortin possibly contaminating rat brain cytosol preparations. On the basis of limited specificity studies of [ 3H]dexamethasone and [ 3H]corticosterone binding under such conditions, it was claimed that binding sites for the two steroids are indistinguishable, and it is thus unnecessary to invoke distinct binding sites for each glucocorticoid [1]. We have extended these competition studies in the presence of Cortisol 17β acid, and shown that in rat hippocampus Type I, corticosterone-preferring glucocorticoid receptors can be clearly distinguished both from transcortin and from Type II, dexamethasone-binding glucocorticoid receptors.

Brain glucocorticoid receptors and their role in behavioural teratogenicity of synthetic glucocorticoids.

The distribution of glucocorticoid receptors (GR) in rat brain during development (postnatal days 3-16) was investigated and the prevalence of GR number was found in the cerebellum, the fastest growing part of perinatal brain. Dexamethasone (D) administration (0.04-3 mg . kg-1 s.c.) in 7-day-old rats induced dose-dependent depletion of brain cytosol GR with a 70% depletion after the smallest dose. Long-term effects of this GR mediated insult (D 1.0 and 0.2 mg . kg-1 s.c.) manifested themselves in adult rats as structural and biochemical brain deviations (especially in the cerebellum and hippocampus), behavioural abnormalities and reproduction disturbances. These sequels were detectable after D doses equal to clinical dosage in obstetrics and neonatology (0.2-0.6 mg . kg-1).

Regulation of glucocorticoid receptors in brain by corticosterone treatment of adrenalectomized rats.

Binding of (3H)-corticosterone in cytosol of hippocampus and hypothalamus has been measured in adrenalectomized (ADX) rats in the presence or absence of corticosterone replacement therapy (suspended shortly before receptor analysis). Corticosterone pellet implantation into female rats or oral corticosterone administration in salinized drinking water given to males for 3 weeks reduced (3H)-corticosterone binding by half in the hippocampus. This reduction was observed whether corticosterone or dexamethasone was employed as competitor to determine nonspecific binding, thus eliminating transcortin as the cause of the corticosterone effect on binding. Scatchard analysis of binding data revealed that the reduction was mostly due to decreased number of receptors. Animals pretreated with corticosterone had a reduction in thymus weight, indicating further the biological effectiveness of the treatment. Further, serum corticosterone in ADX rats pretreated with corticosterone (but with therapy suspended for 24 h) was very low and similar to that of untreated ADX rats. Uptake studies after injection of (3H)-corticosterone intravenously into ADX rats showed that the injected hormone was absent from blood and brain tissues 1 day later, ruling out (in addition to the measurement of serum corticosterone) that the reduction in binding was due to occupation of receptor sites by exogenous corticosterone remaining after withdrawal from therapy. It is suggested that down-regulation of glucocorticoid receptors in brain follows the chronic corticosterone administration. These data are discussed in relation with evidence for down-regulation of other classes of steroid receptors in several tissues, and the consequence that changes in receptor binding in brain may have on the feedback mechanism of corticoids at the central level.

A qualitative comparison of the glucocorticoid receptor in cytosol from human brain and rat brain

The glucocorticoid receptor in cytosol from human brain was studied using isoelectric focussing in slabs of polyacrylamide gel. [ 3H]Dexamethasone was used as tracer for receptor analysis. The glucocorticoid receptor from human brain was compared to the glucocorticoid receptor in rat brain. A similar peak of radioactivity with a pI of about 6.1 was obtained by isoelectric focussing of cytosol from both human brain and rat brain. The trypsin-induced fragmentation patterns of the glucocorticoid receptor from human brain and rat brain were very similar when analyzed by isoelectric focussing. The hormone specificity of the glucocorticoid receptor in human brain and in rat brain cytosol was compared by competition experiments using unlabelled dexamethasone, betamethasone, cortisol and corticosterone as competitors. No difference between human brain and rat brain cytosol was detected. It is concluded that the hormone specificity and the protein structure of the glucocorticoid receptors in human brain and in rat brain are similar.

Role and regulation of brain glucocorticoid receptors

Role and regulation of brain glucocorticoid receptors

Putative estrogen and glucocorticoid receptors in the limbic brain

The brain is a target tissue for both estrogens and adrenal steroids. These hormones alter both neuroendocrine activity and behavior. Putative soluble (cytosol) and cell nuclear receptor sites are concentrated in anterior pituitary and in limbic regions of the brain: hypothalamus, preoptic region, and amygdala for estradiol, and hippocampus, septum, and amygdala for cortieosterone. Recent experiments will be summarized dealing with the following aspects of our work: (1) the postnatal ontogeny of the estradiol-binding system in the limbic brain of the female rat and the temporal relationship of its development to another estradiol-binding protein, probably identical to the α-fetoprotein, which gradually disappears after birth; (2) effects of estradiol on activities of enzymes in pituitary and in brain regions which contain the putative receptors, which effects may relate to the function of the receptor sites; and (3) properties of the putative brain glucocorticoid receptors with particular emphasis on their binding of corticosterone, dexamethasone, and progesterone. Glucocorticoid receptor sites have been studied both in vivo and in vitro using cytosols and tissue slices, thus allowing us to study the cellular mechanism of binding and the extent of receptor occupation by the physiological range of endogenous corticosterone.