Related Experiment Videos
Gonadotropin-releasing hormone requirements for ovulation
F J Karsch1, J M Bowen, A Caraty
1Reproductive Sciences Program and Department of Physiology, University of Michigan, Ann Arbor 48109-0404, USA. fjkarsch@umich.edu
Biology of Reproduction
|February 1, 1997
Summary
Gonadotropin-releasing hormone (GnRH) plays a crucial, deterministic role in ovulation for sheep. A GnRH surge, stimulated by estradiol, is essential for initiating and maintaining the luteinizing hormone (LH) surge, which drives ovulation.
Area of Science:
- Reproductive Endocrinology
- Neuroendocrinology
Background:
- Two models explain GnRH action in ovulation: deterministic (increased GnRH causes LH surge) and permissive (increased pituitary sensitivity to GnRH).
- Rodent and rabbit studies support the deterministic model, while primate studies suggest a permissive role.
Purpose of the Study:
- To investigate the role of GnRH in ovulation in sheep.
- To determine whether GnRH acts deterministically or permissively in the ovine estrous cycle.
Main Methods:
- Analysis of GnRH and LH surge co-occurrence during the preovulatory period.
- Investigation of estradiol's positive feedback effect on GnRH secretion.
- Assessment of GnRH's requirement for LH surge initiation and maintenance.
Main Results:
- A significant GnRH surge was observed concurrently with the preovulatory LH surge in sheep.
- Elevated estradiol levels during the follicular phase positively stimulated the GnRH surge.
- The LH surge's initiation and continuation were dependent on a prompt and sustained increase in GnRH.
Conclusions:
- GnRH functions deterministically in sheep ovulation.
- The GnRH surge is fundamental for generating the LH surge and regulating the estrous cycle in sheep.