Temporal relationship between the onset of daily gonadotrophin surges and of puberty in female golden hamsters.
Daily rhythms of LH and FSH release commence on day 16 or 17 of age in the prepubertal female golden hamster, 2-3 weeks before regular 4-day oestrous cycles begin. We tested the hypothesis that the daily surges of gonadotrophin regulate, at least in part, rate of sexual maturation and, hence, age at puberty. We predict that an advance or a delay in the initiation of the daily rhythm should result in a corresponding advance or delay in the day of puberty. In the first test, the onset of daily gonadotrophin surges was advanced by gonadotrophin-releasing hormone (GnRH) injections; in the second test, the onset was delayed by daily injection of phenobarbital sodium (PB). The day of the first of at least three consecutive post-ovulatory vaginal discharges was used as an index of the age at puberty. Gonadotrophin-releasing hormone (50 ng/0.1 ml saline per animal) was injected at 16.30 h on days 8-17 of age. These injections initiated a daily mid-afternoon surge of LH about 8 days before the onset of the daily rhythm of gonadotrophins in saline-injected controls and the day of first vaginal discharge was advanced by 4 days compared with saline-injected controls (32.0 +/- 1.8 days vs 36.3 +/- 1.0 days; P less than 0.001). Phenobarbital sodium (100 mg/kg body wt), injected at 13.30 h from 16 to 25 days of age, blocked daily surges of gonadotrophin observed in controls by day 18.(ABSTRACT TRUNCATED AT 250 WORDS)
Donham
R S
RS
Creyaufmiller
N
N
Lyons
T J
TJ
Stetson
M H
MH
D000818:Animals; D001835:Body Weight / Q000187:drug effects; D006224:Cricetinae; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood*; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology; D007986:Luteinizing Hormone / Q000097:blood*; D008647:Mesocricetus; D010507:Periodicity; D010634:Phenobarbital / Q000494:pharmacology; D013997:Time Factors
D007987:Gonadotropin-Releasing Hormone; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D010634:Phenobarbital