A circadian egg timer gates ovulation

• Published in: Current biology 2010-03, Vol.20 (6), p.R266-R267
• Main Authors: Sellix, Michael T., Yoshikawa, Tomoko, Menaker, Michael
• Format: Article
• Language: English
• Subjects: Animals; Circadian Rhythm - drug effects; Circadian Rhythm - physiology; Estrus - drug effects; Estrus - physiology; Female; Gonadotropin-Releasing Hormone - administration & dosage; Gonadotropin-Releasing Hormone - analogs & derivatives; Hormone Antagonists - administration & dosage; Luteinizing Hormone - administration & dosage; Luteinizing Hormone - antagonists & inhibitors; Ovulation - drug effects; Ovulation - physiology; Photoperiod; Rats; Receptors, LHRH - antagonists & inhibitors
• ISSN: 0960-9822; 1879-0445
• DOI: 10.1016/j.cub.2010.01.045

Since the pioneering work of Everett and Sawyer, the idea that pituitary gonadotrophins provide the critical timing cue for ovulation has remained unquestioned [1]. It is widely accepted that the timing of ovulation depends entirely on the timing of luteinizing hormone (LH) secretion, itself driven by neuroendocrine releasing factors controlled by the circadian clock in the suprachiasmatic nucleus (SCN) [2,3]. As a consequence, there has been little investigation of a role for the ovary in this process. However, we and others have demonstrated the presence of endogenous circadian clocks in the rat ovary [4–6]. Here we describe a circadian rhythm of ovarian sensitivity to LH that determines the ovulatory response to gonadotrophins. It is plausible that the circadian clock in the ovary may set the responsiveness of the ovarian follicle to the LH surge. Our results significantly alter the classic view that gonadotrophins provide the only timing cue for ovulation. They suggest that the ovary itself plays a major role in the process and provide a new perspective that will inform future research on infertility and ovarian physiology.