Glucocorticoid regulation of proopiomelanocortin mRNA levels in rat arcuate nucleus.
The role of glucocorticoids in the regulation of proopiomelanocortin (POMC) mRNA levels in the hypothalamus was studied in different areas of the arcuate nucleus using quantitative in situ hybridization. The arcuate nucleus was arbitrarily divided into four regions in a rostral to caudal plane and the levels of mRNA were measured by optical densitometry. Adrenalectomy produced a marked decrease in the hybridization signal in the entire arcuate nucleus, the effect being less striking in the most rostral subdivision of the arcuate nucleus. Dexamethasone treatment completely reversed the adrenalectomy-induced decrease in POMC mRNA concentration. Moreover, in the most caudal regions of the arcuate nucleus, dexamethasone treatment produced an increase in mRNA which reached levels higher than those observed in intact animals. In the anterior pituitary gland, as previously reported, adrenalectomy produced an increase in POMC mRNA levels, an effect which was completely prevented by the administration of dexamethasone. These results suggest that POMC is differentially regulated by glucocorticoids in the anterior pituitary and the hypothalamus.
Tong
Y
Y
MRC Group in Molecular Endocrinology, CHUL Research Center, Laval University Medical Centre, Quebec, Canada G1V 4G2.
Couët
J
J
Simard
J
J
Pelletier
G
G