Depletion of Hypothalamic Growth Hormone-Releasing Hormone by Neonatal Monosodium Glutamate Treatment Reveals an Inhibitory Effect of Betamethasone on Growth Hormone Secretion in Adult Rats
作者:
Roger Corder,
Patrick Saudan,
Musalnah Mazlan,
Charles McLean,
Rolf C. Gaillard,
期刊:
Neuroendocrinology
(Karger Available online 1990)
卷期:
Volume 51,
issue 1
页码: 85-92
ISSN:0028-3835
年代: 1990
DOI:10.1159/000125321
出版商: S. Karger AG
关键词: Growth;Glucocorticoid;Glucocorticoid receptor;Somatostatin;Growth hormone-releasing hormone;Arcuate nucleus
数据来源: Karger
摘要:
Rats were treated with monosodium glutamate (MSG), 4 mg/g on alternate days for the first 10 days of life, to induce lesions of the arcuate nucleus and destroy the majority of growth hormone-releasing hormone (GHRH) neurones. At 10 weeks of age, control (n = 42) and MSG-treated (n = 36) male rats were used to test the effect of glucocorticoids on growth hormone (GH) secretion. Each treatment group was divided into six study groups to determine the effect of betamethasone (BM), administered either 3 or 20 h prior to sacrifice, alone and in combination with hypoglycaemia (insulin 0.1 U/100 g). BM treatment of male rats was without effect on plasma GH levels in control animals. In contrast, glucocorticoid administered either 3 h before sacrifice or the previous evening significantly reduced circulating GH (p < 0.001) in MSG-treated animals. The difference in plasma GH response to BM pretreatment in control rats and those with lesions of the arcuate nucleus indicates a hypothalamic action of glucocorticoids, presumably on somatostatin and GHRH neurones. In control animals the effects appear to be counterbalancing, but following destruction of GHRH neurones an uncompensated inhibitory influence was observed. Male MSG-treated rats had lower body weight (–25%) and reduced hypothalamic GHRH (–89%) and pituitary GH content (–69%) compared to male controls. Female rats which had undergone the same neonatal MSG treatment (n = 40) when sacrificed 1 week after their male counterparts showed similar reductions in body weight (–15%), hypothalamic GHRH (–74%), and pituitary GH (–67%). Interestingly, the hypothalamic concentration of GHRH in control female rats (n = 39) was only 41% of male controls, suggesting an important effect of sex hormones on GH
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