Cortisol Reduces Gonadotropin-Releasing Hormone Pulse Frequency in Follicular Phase Ewes: Influence of Ovarian Steroids
Amy E Oakley, Kellie M Breen, Iain J Clarke, Fred J Karsch, Elizabeth R Wagenmaker, Alan J Tilbrook
ENDOCRINOLOGY | ENDOCRINE SOC | Published : 2009
Stress-like elevations in plasma glucocorticoids suppress gonadotropin secretion and can disrupt ovarian cyclicity. In sheep, cortisol acts at the pituitary to reduce responsiveness to GnRH but does not affect GnRH pulse frequency in the absence of ovarian hormones. However, in ewes during the follicular phase of the estrous cycle, cortisol reduces LH pulse frequency. To test the hypothesis that cortisol reduces GnRH pulse frequency in the presence of ovarian steroids, the effect of cortisol on GnRH secretion was monitored directly in pituitary portal blood of follicular phase sheep in the presence and absence of a cortisol treatment that elevated plasma cortisol to a level observed during s..View full abstract
Awarded by National Institutes of Health
Awarded by EUNICE KENNEDY SHRIVER NATIONAL INSTITUTE OF CHILD HEALTH &HUMAN DEVELOPMENT
Awarded by NATIONAL INSTITUTE OF GENERAL MEDICAL SCIENCES
We thank Doug Doop and Gary McCalla for their exceptional animal care, Andrew V. Pytiak and Alison P. Cooper for their technical assistance, and Drs. Alain Caraty, Gordon D. Niswender, and Leo E. Reichert, Jr., for supplying RIA reagents.Address all correspondence and requests for reprints to: Fred J. Karsch, Department of Molecular and Integrative Physiology, University of Michigan, 1301 East Catherine Street, Room 7744 Sci II 0622, Ann Arbor, Michigan 48109. E-mail: firstname.lastname@example.org.This work was supported by National Institutes of Health Grants HD30773, T32-07048, and T32-08322.Present address for K. M. B.: Department of Reproductive Medicine, University of California, San Diego, Leichtag Biomedical Research Building, Room 349, La Jolla, California 92093-0674.Present address for A. E. O.: Department of Physiology and Biophysics, University of Washington, Box 356460, 1959 Northeast Pacific Street, Health Sciences Building, Room BB604, Seattle Washington 98195-6460.The preliminary report has appeared in 2007 Biol Reprod 74 ( Suppl 1, Abstract 429).Disclosure Statement: The authors have nothing to declare.