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Site-specific decrease of progesterone receptor mRNA expression in the hypothalamus of middle-aged persistently
Richard H Mills1, Horacio E Romeo, John K H Lu
1Department of Neurobiology, UCLA School of Medicine, Los Angeles, CA 90095-1763, USA. rhmills@ucla.edu
Brain Research
|November 7, 2002
Summary
Aging female rats develop persistent estrus (PE) due to reduced hypothalamic progesterone receptors (PR). This impacts luteinizing hormone (LH) regulation, explaining the loss of reproductive cycles in long-term PE.
Area of Science:
- Neuroendocrinology
- Reproductive Biology
- Aging Research
Background:
- Middle-aged females can enter a persistently estrus (PE) state, characterized by acyclicity.
- Early PE rats respond to progesterone, while long-term PE rats do not, suggesting a hormonal regulatory breakdown.
Purpose of the Study:
- To investigate the role of hypothalamic progesterone receptor (PR) expression in the development of persistent estrus (PE) in aging female rats.
- To test the hypothesis that diminished estrogen-induced PR expression in the hypothalamus prevents progesterone from stimulating luteinizing hormone (LH) release.
Main Methods:
- Quantitative measurement of PR mRNA levels in specific hypothalamic regions (AVPV, VMH, ARH, MPN) of young, early PE, and long-term PE rats.
- Comparison of PR mRNA levels across different age groups and reproductive states.
Main Results:
- Decreased PR mRNA levels were observed in the anteroventral periventricular nucleus (AVPV) of both early and long-term PE rats compared to proestrus rats.
- PR mRNA levels were reduced in the ventromedial nucleus (VMH) and arcuate nucleus (ARH) only in long-term PE rats.
- PR mRNA levels in the medial preoptic nucleus (MPN) remained unchanged across all groups.
Conclusions:
- Reduced hypothalamic PR expression, particularly in the AVPV, is associated with the acyclicity observed in early persistent estrus (PE).
- Diminished estrogen-induced PR expression in the hypothalamus correlates with the inability of long-term PE rats to respond to progesterone, leading to acyclicity.