Changes in the Hypothalamo-Corticotrope Axis after Bilateral Adrenalectomy: Evidence for a Median Eminence Site of Glucocorticoid Action

Spinedi, Eduardo; Giacomini, Marco; Jacquier, Marie-Claude; Gaillard, Rolf C.

doi:10.1159/000125713

Cited by 80 publications

(81 citation statements)

References 38 publications

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“…In addition, the lack of feedback effects at the CRF peptide level in the ME suggests that, in chickens, glucocorticoids do not influence the secretion of CRF from the ME. The latter is in contrast to the mammalian situation, where the ME seems to be an important site of glucocorticoid action (Jones et al 1977, Keller-Wood & Dallman 1984, Spinedi et al 1991, Feldman et al 1992, Feldman & Weidenfeld 2002. The decrease in CRF content seen in the diencephalon during the first hour after in vivo treatment with corticosterone could be caused by the stress of handling.…”

Section: Discussionmentioning

confidence: 97%

“…Glucocorticoids have been found to regulate CRF mRNA at two sites, by inhibiting gene transcription and by decreasing the mRNA stability (Ma et al 2001). In addition, glucocorticoids were also shown to influence the stimulus-evoked secretion of CRF from the median eminence (ME) (Spinedi et al 1991). At the level of the pituitary, glucocorticoids have been shown to have an effect on ACTH secretion (Dallman et al 1987) and a direct inhibitory effect via the GR on the proopiomelanocortin (POMC) mRNA level (Eberwine & Roberts 1984).…”

Section: Introductionmentioning

confidence: 99%

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Corticosterone-induced negative feedback mechanisms within the hypothalamo–pituitary–adrenal axis of the chicken

Vandenborne

Groef²,

Geelissen³

et al. 2005

Journal of Endocrinology

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This paper reports the results of in vivo and in vitro experiments on the feedback effects of corticosterone on the hypothalamo-pituitary-adrenal axis in embryos at day 18 of incubation and in 9-day-old chickens. In vivo, a significant negative feedback was detected on the levels of corticotropin-releasing factor (CRF) precursor (proCRF) mRNA and on the plasma concentration of corticosterone, two hours after a single intravenous injection with 40 µg corticosterone. In contrast, the levels of CRF peptide in the hypothalamic area, the CRF receptor type 1 (CRF-R1) mRNA and pro-opiomelanocortin (POMC) mRNA levels in the pituitary were not affected by the in vivo administration of corticosterone. In vitro, incubation with 1 µM corticosterone did not affect the CRF-R1 mRNA levels in the pituitary, but significant feedback inhibition was observed on the POMC mRNA levels. These in vitro effects were the same at the two ages studied. The in vitro feedback effect on the proCRF gene expression, however, differed with age. In 9-day-old animals a decrease in gene expression was observed which was not detectable in embryonic tissue at day 18 of the ontogeny.

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Section: Discussionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Corticosterone-induced negative feedback mechanisms within the hypothalamo–pituitary–adrenal axis of the chicken

Vandenborne

Groef²,

Geelissen³

et al. 2005

Journal of Endocrinology

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“…Mild stress was induced by an intraperitoneal saline injection. Plasma corticosterone was evaluated by radioimmunoassay (18).…”

Section: Vol 26 2006mentioning

confidence: 99%

GLUT8 Is Dispensable for Embryonic Development but Influences Hippocampal Neurogenesis and Heart Function

Membrez

Hummler

Beermann³

et al. 2006

Molecular and Cellular Biology

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GLUT8 is a glucose transporter isoform expressed at high levels in testis; at intermediate levels in the brain, including the hippocampus; and at lower levels in the heart and several other tissues. GLUT8 is located in an intracellular compartment and does not appear to translocate to the cell surface, except in blastocysts, where insulin has been reported to induce its surface expression. Here, we generated mice with inactivation of the glut8 gene. We showed that expression of GLUT8 was not required for normal embryonic development and that glut8 ؊/؊ mice had normal postnatal development, glucose homeostasis, and response to mild stress. Adult glut8 ؊/؊ mice showed increased proliferation of hippocampal cells but no defect in memory acquisition and retention. Absence of GLUT8 from the heart did not alter heart size and morphology but led to an increase in P-wave duration, which was not associated with abnormal Nav1.5 Na ؉ channel or connexin expression. Thus, absence of GLUT8 expression in the mouse caused complex but mild physiological alterations.

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“…Within-and between-assay variability averaged less than 10%. Corticosterone concentrations were determined in duplicate using a single antibody/charcoal/dextran method (Spinedi et al 1991). Blood samples were extracted using dichloromethane.…”

Section: Radioimmunoassaymentioning

confidence: 99%

Effects of repeated doses and continuous infusions of the growth hormone-releasing peptide hexarelin in conscious male rats

Conley

Gaillard²,

Giustina³

et al. 1998

Journal of Endocrinology

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We have previously shown that hexarelin, a novel GHreleasing peptide (GHRP), is able to elicit GH release when administered i.v., s.c. or by mouth and that it is a more potent GH secretagogue than GHRP-6. In the current study, we investigated the effects of hexarelin administered as repeated doses at 2 h intervals or as a continuous 6, 30 or 174 h infusion to conscious male rats.In the first experiment, adult male Sprague-Dawley rats were prepared with dual indwelling jugular catheters. On the day of experimentation, these animals received three 25 µg/kg i.v. boluses of hexarelin at 2 h intervals with blood sampling at 5, 10, 15, 30, 60, 90 and 120 min after each dose. The mean peak GH response and the mean area under the GH response curve (AUC) for the 30 min after each administration were calculated and are reported as the mean ... For both the peak and AUC results there was a significant (P<0·05) difference in the GH response noted between the first (peak 301 37 ng/ml; AUC 5585 700 ng/ml per 30 min) and second (peak 149 47 ng/ml; AUC 3056 908 ng/ml per 30 min) injections of hexarelin, but not between the first and third (peak 214 49 ng/ml; AUC 3862 844 ng/ml per 30 min). In a second series of experiments, adult male Sprague-Dawley rats received continuous infusions (100 µg/h) of hexarelin or saline (1 ml/h) for 6, 30 or 174 h. Blood samples were collected every 20 min for the duration of the 6 h infusion and for the last 6 h of the two longer hexarelin infusions. Plasma GH concentrations peaked within 40 min of the initiation of infusion, but soon returned to basal levels. Mean plasma GH concentrations did not differ between any of the treatment groups, nor did any of the parameters of pulsatile hormone release analyzed. No significant differences in plasma corticosterone concentrations were noted between any of the treatment groups. On the other hand, while neither the 6 h (941 70 ng/ml) nor the 30 h (954 70 ng/ml) hexarelin infusions resulted in a significant increase in the plasma IGF-I concentrations over those noted in the saline controls (935 65 ng/ml), a 174 h hexarelin infusion did elicit a significant increase (1289 42 ng/ml; P<0·05). Thus it appears that, while continuous exposure to hexarelin does not disrupt normal GH cycling, it may (after up to 174 h of exposure) alter other components of the growth axis. In addition, since the character of pulsatile GH release remained unaltered in response to the hexarelin infusion, it appears that this GHRP may not act by suppression of functional somatostatin tone as has been suggested previously.

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Changes in the Hypothalamo-Corticotrope Axis after Bilateral Adrenalectomy: Evidence for a Median Eminence Site of Glucocorticoid Action

Cited by 80 publications

References 38 publications

Corticosterone-induced negative feedback mechanisms within the hypothalamo–pituitary–adrenal axis of the chicken

Corticosterone-induced negative feedback mechanisms within the hypothalamo–pituitary–adrenal axis of the chicken

GLUT8 Is Dispensable for Embryonic Development but Influences Hippocampal Neurogenesis and Heart Function

Effects of repeated doses and continuous infusions of the growth hormone-releasing peptide hexarelin in conscious male rats

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