Absence of increased neuropeptide Y neuronal activity before and during the luteinizing hormone (LH) surge may underlie the attenuated preovulatory LH surge in middle-aged rats

Endocrinology
A Sahu, S P Kalra

Abstract

A large body of evidence suggests that the neuroendocrine axis plays a major role in the reproductive aging of female rats. Since increased hypothalamic neuropeptide Y (NPY) neurosecretion is crucial in the preovulatory LH discharge in young rats, we tested the hypothesis that diminution in the preovulatory LH surge in middle-aged (MA) rats may be due to altered neurosecretory activity in NPYergic neurons. In Exp 1, we examined NPY levels in six microdissected hypothalamic nuclei, including median eminence (ME), arcuate nucleus (ARC), and medial preoptic area (MPOA), at 1000, 1200, 1400, 1600, 1800, 2000, or 2200 h on the day of proestrus in young (2.5- to 3-month old) and MA (7- to 9-month old) regularly cycling rats. At 1000 h, ME NPY levels in young rats were significantly lower than those in MA rats. In young rats, the ME NPY levels were significantly increased at 1400 h before the LH surge in the afternoon and thereafter decreased progressively during the interval of the LH surge. In MA rats, however, ME NPY levels decreased in the afternoon in association with an attenuated LH surge. In addition, in the ARC and MPOA, the other hypothalamic sites associated with induction of LH surge, NPY levels increased before and during...Continue Reading

References

Jan 1, 1990·Annals of the New York Academy of Sciences·G Pelletier
Nov 1, 1990·Brain Research Bulletin·B D WhiteR J Martin
May 1, 1988·DNA·P E DanielsonJ G Sutcliffe
Jan 1, 1985·Neurobiology of Aging·B S RubinR S Bridges
Sep 10, 1984·Life Sciences·S P Kalra, W R Crowley
Jan 1, 1980·Cell and Tissue Research·I MerchenthalerG Sétáló
Oct 1, 1980·Biology of Reproduction·R L CooperR F Walker

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Citations

Nov 4, 2004·Experimental Biology and Medicine·Tandra R Chakraborty, Andrea C Gore
Jun 10, 2000·American Journal of Physiology. Regulatory, Integrative and Comparative Physiology·A A AmmarP Södersten

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