Document Detail

Site-specific decrease of progesterone receptor mRNA expression in the hypothalamus of middle-aged persistently estrus rats.
MedLine Citation:
PMID:  12419537     Owner:  NLM     Status:  MEDLINE    
Middle-aged females gradually become acyclic and spontaneously develop a persistently estrus (PE) state. PE rats, acyclic for 30 days (early PE), are unresponsive to the positive feedback action of estrogen, but respond to a progesterone challenge with a luteinizing hormone (LH) surge and ovulation; unlike long-term PE rats, acyclic for 90 days, neither estrogen nor estrogen plus progesterone will elicit an LH surge [10th International Congress of Endocrinology, San Francisco, P3 (1996) 1061]. We hypothesize that the PE state may develop due to a diminished level of estrogen-induced progesterone receptor (PR) expression in the hypothalamus that prevents progesterone from stimulating LH regulating circuits. To test this hypothesis, PR mRNA levels were measured in hypothalamic regions of young, proestrus (2-3 months of age), early PE (10-12 months) and long-term PE (13-15 months) rats. The anteroventral periventricular nucleus (AVPV), an important regulatory site of the LH surge, had decreased PR mRNA levels in early and long-term PE rats compared with proestrus rats. However, PR mRNA levels were reduced only in long-term PE rats in the ventromedial nucleus (VMH) and arcuate nucleus (ARH). In the medial preoptic nucleus (MPN), levels of PR mRNA did not change. A previous report showed that exogenous progesterone stimulates an LH surge in young and early PE animals, indicating that the expression of PR mRNA demonstrated in this study is sufficient to mediate progesterone facilitation of the LH surge in early PE rats. In acyclic, long-term PE rats, diminished estrogen-induced expression of progesterone receptors is correlated with a previously shown inability to respond to exogenous progesterone.
Richard H Mills; Horacio E Romeo; John K H Lu; Paul E Micevych
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Brain research     Volume:  955     ISSN:  0006-8993     ISO Abbreviation:  Brain Res.     Publication Date:  2002 Nov 
Date Detail:
Created Date:  2002-11-06     Completed Date:  2003-01-31     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0045503     Medline TA:  Brain Res     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  200-6     Citation Subset:  IM    
Department of Neurobiology, UCLA School of Medicine, Los Angeles, CA 90095-1763, USA.
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MeSH Terms
Aging / genetics,  metabolism*
Estrus / genetics,  metabolism*
Gene Expression Regulation / physiology*
Hypothalamus / metabolism*
RNA, Messenger / biosynthesis*
Rats, Long-Evans
Receptors, Progesterone / biosynthesis*,  genetics
Grant Support
Reg. No./Substance:
0/RNA, Messenger; 0/Receptors, Progesterone

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