The estrous cycle in golden hamsters: A circadian pacemaker times preovulatory gonadotropin release

✍ Scribed by Stetson, Milton H. ;Gibson, Jeffrey T.

• Book ID: 102892471
• Publisher: John Wiley and Sons
• Year: 1977
• Tongue: English
• Weight: 601 KB
• Volume: 201
• Category: Article
• ISSN: 0022-104X
• DOI: 10.1002/jez.1402010212

✦ Synopsis

Abstract

In a population of cycling female hamsters entrained to an LD 6:18 light cycle (lights 1000–1600 hours), preovulatory release of luteinizing hormone and follicle‐stimulating hormone occurred in some animals at 1300–1400 hours and in others at 1900 hours. In every case peak release was phase‐locked (2–3‐hour positive phase angle) to the circadian rhythm of locomotor activity. The pattern of entrainment of gonadotropin release on LD 6:18 is fully explicable in terms of the hamster's phase response curve to light. We conclude that periodic gonadotropin release in cycling females is timed by a circadian oscillator (biological clock) that is probably the same oscillator driving the circadian rhythm of locomotor activity.