Glucocorticoid receptor (GR) antagonism may be of considerable therapeutic value in stress-related psychopathology such as depression. However, blockade of all GR-dependent processes in the brain will lead to unnecessary and even counteractive effects, such as elevated endogenous cortisol levels. Selective GR modulators are ligands that can act both as agonist and as antagonist and may be used to separate beneficial from harmful treatment effects. We have discovered that the high-affinity GR ligand C108297 is a selective modulator in the rat brain. We first demonstrate that C108297 induces a unique interaction profile between GR and its downstream effector molecules, the nuclear receptor coregulators, compared with the full agonist dexamethasone and the antagonist RU486 (mifepristone). C108297 displays partial agonistic activity for the suppression of hypothalamic corticotropin-releasing hormone (CRH) gene expression and potently enhances GR-dependent memory consolidation of training on an inhibitory avoidance task. In contrast, it lacks agonistic effects on the expression of CRH in the central amygdala and antagonizes GR-mediated reduction in hippocampal neurogenesis after chronic corticosterone exposure. Importantly, the compound does not lead to disinhibition of the hypothalamus-pituitary-adrenal axis. Thus, C108297 represents a class of ligands that has the potential to more selectively abrogate pathogenic GR-dependent processes in the brain, while retaining beneficial aspects of GR signaling.HPA axis | neuroendocrinology | steroid pharmacology | transcription regulation | NCoA1

Adaptation to stress in vertebrates occurs via activation of hormonal and neuronal signaling cascades in which corticotropinreleasing hormone (CRH) plays a central role. Expression of brain CRH is subject to strong, brain-region specific regulation by glucocorticoid hormones and neurogenic intracellular signals. We hypothesized that Steroid Receptor Coactivator 1 (SRC-1), a transcriptional coregulator of the glucocorticoid receptor, is involved in the sensitivity of CRH regulation by stress-related factors. In the brains of SRC-1 knockout mice we found basal CRH mRNA levels to be lower in the central nucleus of the amygdala. Hypothalamic CRH up-regulation after chronic (but not acute) stress, as well as region-dependent up-and down-regulation induced by synthetic glucocorticoids, were significantly attenuated compared with wild type. The impaired induction of the crh gene by neurogenic signals was corroborated in AtT-20 cells, where siRNA and overexpression experiments showed that SRC-1 is necessary for full induction of a CRH promoter reporter gene by forskolin, suggestive of involvement of transcription factor CREB. In conclusion, SRC-1 is involved in positive and negative regulation of the crh gene, and an important factor for the adaptive capacity of stress.adaptation ͉ amygdala ͉ HPA axis ͉ neuroendocrinology ͉ transcription B rain corticotropin-releasing hormone (CRH) plays a pivotal role in the mammalian response to stress. CRH synthesized by neurons in the central nucleus of the amygdala (CeA) mediates the effect of stress on emotional states, including fear and anxiety (1, 2). From the paraventricular nucleus of the hypothalamus (PVN) CRH coordinates autonomic outflow and the activity of the hypothalamus-pituitary-adrenal (HPA) axis. The latter leads to secretion of the adrenal glucocorticoid hormones, which in turn orchestrate the adaptation to stress of virtually all tissues in the body (3-5).As part of adaptation, CRH expression itself is strongly regulated in response to stress-induced elevations of glucocorticoids and neurogenic signals. In the core of the HPA-axis, activation of the glucocorticoid receptor (GR) can repress transcription from the crh gene as part of negative feedback, whereas stress-related noradrenergic and glutamatergic excitatory signals can activate the gene, in part via activation of the transcription factor CREB. In the CeA, both GR activation and excitatory signals can lead to an increased CRH expression (6, 7). These modulations are considered crucial for stress adaptation, and a considerable amount of research has been devoted to understand how transcriptional signals are integrated at the level of the CRH promoter, both in vitro and in vivo (8, 9). Nevertheless, the regulation of the crh gene in vivo is far from understood.Transcriptional coregulators constitute an expanding class of molecules that act as mediators and integrators of signals carried by nuclear receptors, such as GR (10). The p160 coregulator Steroid Receptor Coactivator (SRC-1) is strongly expressed in br...

The effects of discontinuation and restoration of ovarian influences on the pituitary LH response to LHRH in vitro were investigated. When female rat pituitary glands taken on day 2 of dioestrus were incubated with LHRH the release of LH was low during the first hour (lag phase response) and afterwards a progressive, protein synthesis-dependent increase took place (second phase response), this being the self-priming action of LHRH. Short-term discontinuation (less than 1 day) of ovarian influences on the rat pituitary gland in vivo (ovariectomy) or in vitro (incubation in medium only) resulted in an increased LHRH-induced LH response during the lag phase. The biphasic LH response or the self-priming action of LHRH disappeared completely after long-term discontinuation of ovarian influences on the pituitary gland, LH release being at its maximum from the start of the incubation. The biphasic response was reinstated when ovaries were implanted under the kidney capsules of ovariectomized rats. Auto-implantation of an ovary into the spleen immediately after bilateral ovariectomy did not, however, prevent the disappearance of the LHRH self-priming action. Ovarian activity responsible for the presence of the low LH response during the lag phase was thus effectively removed by the liver, but inhibin-like activity suppressing serum FSH levels remained present. Silicone elastomer implants (s.c.) containing oestradiol-17 beta, implanted for 4 weeks, did not reverse the loss of the biphasic LH response to LHRH. It is concluded that liver-labile factors released by the ovaries keep the pituitary gland in a state of low responsiveness to LHRH.(ABSTRACT TRUNCATED AT 250 WORDS)

The hypothesis that LH-RH induces LH release partly through a protein synthesis dependent step (protein factor) was further investigated using two different experimental designs. First, during incubation of pituitary glands of intact dioestrous female rats with a maximally active concentration of LH-RH, the inhibitor of protein synthesis cycloheximide was added at various times after the beginning of the incubation. The results show that it takes a relatively long time, i.e. more than 1 h of exposure to LH-RH before the amount of the protein factor has increased sufficiently to allow a maximal LH secretion. Secondly, LH-RH was injected iv after which the protein factor was assayed by incubating the pituitary glands with a maximally active concentration of LH-RH in the presence of cycloheximide and measuring LH release in vitro. It was found that 1 h after the injection sufficient protein factor was present to permit an elevated response to LH-RH. This response could be suppressed by injecting cycloheximide prior to LH-RH. When the interval between injection of LH-RH and beginning of the incubation was increased to 2 h, LH release in vitro decreased again. However, ovariectomy immediately before LH-RH injection resulted in maintenance of the elevated response to LH-RH in vitro, indicating a role of the ovaries in this phenomenon.

Gonadotrophin treatment reduces VEGF(120) expression which may have serious consequences for normal embryonic development. The present data cannot establish whether this effect is a cause or consequence of delayed implantation.