Related Experiment Videos
The central oxytocin pulse generator: a pacemaker for the ovarian cycle
J A McCracken1, E E Custer, J A Eldering
1Worcester Foundation for Biomedical Research, Shrewsbury, MA 01545, USA.
Acta Neurobiologiae Experimentalis
|January 1, 1996
Summary
Estradiol and progesterone withdrawal trigger oxytocin pulses, stimulating prostaglandin F2 alpha release. This establishes a new hypothalamic-posterior pituitary-gonadal axis for terminating the ovarian cycle.
Area of Science:
- Reproductive Endocrinology
- Neuroendocrinology
- Ovarian Physiology
Background:
- Luteolysis involves episodic oxytocin (OT) and prostaglandin F2 alpha (PGF2 alpha) pulses.
- The corpus luteum (CL) and neurohypophysis contribute to OT release.
- Endometrial OT receptors mediate PGF2 alpha stimulation.
Purpose of the Study:
- To differentiate the contributions of neurohypophysial and luteal OT to luteolysis.
- To investigate the hormonal regulation of oxytocin pulse generation.
- To elucidate the hormonal axis involved in ovarian cycle termination.
Main Methods:
- Ovariectomized sheep received estradiol-17 beta (E) and progesterone (P) to mimic cyclical levels.
- Intact sheep underwent luteectomy to remove the CL and initiate P withdrawal.
- Hormonal levels and pulse patterns were monitored in response to E and P manipulation.
Main Results:
- Increased E levels or P withdrawal induced episodic high-frequency OT pulses.
- These OT pulses initiated subluteolytic PGF2 alpha release, triggering further luteal OT secretion.
- Luteal OT amplified PGF2 alpha secretion, leading to luteolysis.
Conclusions:
- Estradiol increases stimulate the central OT pulse generator frequency.
- A positive feedback loop exists between luteal OT and uterine PGF2 alpha secretion.
- Evidence supports a hypothalamic-posterior pituitary-gonadal axis for ovarian cycle termination via OT.