Synchronizing Effect of Photoperiodicity on Ovulation in Hamsters<sup>1</sup>

Alleva, John J.; Waleski, Mary V.; Alleva, Frederic R.; Umberger, Ernest J.

doi:10.1210/endo-82-6-1227

Cited by 39 publications

(10 citation statements)

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“…Irregularities developed in the estrous cycles of some animals maintained in LL; this was expected from earlier reports (16,17) and presented a further opportunity to assess the relation of the circadian system to estrous cyclicity. In no instance was a normal 4-day estrous cycle observed in hamsters with disrupted circadian activity rhythms (n = 6), although it must be noted that a rigorous analysis of the disrupted estrous rhythm was not attempted because daily tests for lordosis influence wheel-running activity.…”

Section: Resultsmentioning

confidence: 52%

See 1 more Smart Citation

Circadian organization of the estrous cycle of the golden hamster.

Fitzgerald¹,

Zucker²

1976

Proc. Natl. Acad. Sci. U.S.A.

100

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In constant dim illumination the hamster estrous cycle free-runs with a period that is a quadruple multiple of the concurrently recorded rhythm of wheel-running activity; both activity and estrous cycles are generated by biological clocks. Maintenance of stable phase angle differences between heat onset and running onset before and after treatment with deuterium oxide suggests that a common circadian system generates periodicities in estrus and activity. An organization of the estrous cycle is proposed in which the stimulus for the ovulatory surge of luteinizing hormone is generated by a circadian system that includes the suprachiasmatic nuclei of the hypothalamus. Various possible interactions of estradiol and photoperiod with the neurogenic stimulus for the luteinizing hormone surge are described and implications of different types of circadian organization of the estrous cycle for theories of sexual differentiation are considered. Estrous and menstrual cycles are readily detectable in a wide variety of spontaneously ovulating polycyclic mammals (1, 2) and were among the first hormonally related rhythms described (3). Typically, the interval between successive recurrences of ovulation, behavioral receptivity (estrus), or release of pituitary ovulating hormone is relatively constant and species specific.Female reproductive cycles depend upon rhythmic release of hormones from the anterior pituitary. The underlying basis for this phenomenon "remains one of the more poorly understood phenomena in regulatory biology" (ref. 4, p. 607). One exciting possibility is that these cycles are manifestations of biological clocks, defined as endogenous self-sustained oscillators specialized for time measurement (5, 6). If one were to establish the clock-like nature of the mechanism underlying the mammalian estrous cycle, then studies of reproductive phenomena could benefit from substantial theoretical and empirical generalizations of the discipline of biochronometry (6).To establish that an observed rhythm is the manifestation of a biological clock it is adequate to demonstrate that the rhythm persists under constant environmental conditions with a period that differs significantly from that under entrained conditions. This has been accomplished for the estrous rhythm of one mammal. In a landmark study, Alleva et al. (7) observed that the period of the hamster estrous cycle was 96 hr when the animals were exposed to a 16 hr light:8 hr dark (LD 16:8) cycle; in constant illumination (LL), the estrous cycle persisted, with 18 of the 20 animals generating periods that differed significantly from 96 hr (range of 95. 35-97.54 hr). This approximately 4-day cycle (a circaquadridian rhythm) established the endogenous nature of the hamster estrous cycle. Alleva et al. (7) speculated that the clock for the estrous cycle functioned with a circadian rather than a circaquadridian frequency. This hypothesis is supported by several lines of evidence; e.g., spontaAbbreviations: LH, luteinizing hormone (lutropin); GnRH, gonadotrophin r...

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Section: Resultsmentioning

confidence: 52%

“…1 (15). The period of the hamster estrous cycle is thus a multiple (X4) of the circadian running rhythm, both under free-running conditions and in the entrained state (7).…”

Section: Resultsmentioning

confidence: 99%

Circadian organization of the estrous cycle of the golden hamster.

Fitzgerald¹,

Zucker²

1976

Proc. Natl. Acad. Sci. U.S.A.

100

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“…Similarly in females, where puberty occurs during the fifth week (Alleva, et a!., 1968), blinding or exposure to short-day photoperiods had no apparent effect during the first 7 weeks of age, the rate of estrogen dependent uterine growth being similar in all treatment groups.…”

Section: Discussionmentioning

confidence: 79%

Influence of Photoperiod on Reproductive Development in the Golden Hamster

Darrow¹,

Davis²,

Elliott³

et al. 1980

Biology of Reproduction

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The effect of early lighting conditions on the sexual development of male and female golden hamsters was investigated, utilizing two experimental paradigms. In the first, hamsters were ex posed to one of several daily light cyc!es (14L:1OD, 6L:18D, 1L:23D, or constant darkness) from birth to 7 weeks of age. Weekly measurements of gonadal and sex accessory organ weights demon strated similar rates of reproductive development among treatment groups, indicating that the onset of puberty is not photoperiodically controlled. In the second experiment, hamsters blinded

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“…In the female rat for in stance, the LH surge has a 24-hour periodicity and constant estrogen stimulation can induce daily LH peaks [10,16,30], The LH surge and ovulation in female rats and hamsters are synchronized to the light-dark cycle [2,12]. Whether female rodents show diurnal changes in their behavioral receptivity is controversial, however.…”

Section: Introductionmentioning

confidence: 99%

Characterization of a Pineal-Independent Diurnal Rhythm in Neural Estrogen Receptors and Its Possible Behavioral Consequences

et al. 1983

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We have previously reported a diurnal variation in brain cytoplasmic estrogen receptors in female rats in the absence of circulating estrogens. In this report we characterize this diurnal rhythm. Levels of cytoplasmic estrogen receptors are greater during light periods than during dark periods in the hypothalamus and in the preoptic area of ovariectomized (OVX) rats. A similar diurnal variation in cytoplasmic receptor content is also found in the brains of female hamsters, but no light-dark differences are seen in the brains of castrated male rats. β-Adrenergic blockade, which inhibits pineal function, had a marginal effect on receptor concentration during the dark. However, pinealectomy did not alter light-dark differences in receptor concentration. The behavioral consequences of the diurnal fluctuations in levels of cytoplasmic estrogen receptors were investigated. Seven different estrogen regimens were administered to OVX female rats at light and dark time points; progesterone was injected 5 h before behavioral testing. Six estrogen paradigms providing comparable hormonal stimuli in the light and dark failed to induce diurnal differences in sexual receptivity. One estrogen regimen consisting of a Silastic capsule of unesterified estradiol in oil followed 24 h later by a pulse of estradiol induced higher levels of sexual receptivity when treatment began during dark periods than during light periods. In parallel experiments nuclear estrogen receptor levels were measured by exchange assay 4 h after Silastic capsules were implanted. Higher levels of nuclear receptors were found during dark periods compared to light periods. Light-dark differences in nuclear translocation of receptors and behavioral sensitivity to estrogen are probably a consequence of light-dark differences in release of estradiol from Silastics resulting in light-dark differences in serum estradiol. Since these serum levels of hormone are quite low (less than 3 pg/ml), the effectiveness of the Silastic-pulse paradigm suggests the importance of small early changes of estradiol levels during the estrous cycle and supports a two-phase mechanism of estrogen action. Saturating doses of estradiol produce similar levels of brain nuclear estrogen receptors whether administered at light or dark time points. Thus, cytoplasmic estrogen receptor content is not indicative of the functional effectiveness of the receptors.

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Synchronizing Effect of Photoperiodicity on Ovulation in Hamsters¹

Cited by 39 publications

References 0 publications

Circadian organization of the estrous cycle of the golden hamster.

Circadian organization of the estrous cycle of the golden hamster.

Influence of Photoperiod on Reproductive Development in the Golden Hamster

Characterization of a Pineal-Independent Diurnal Rhythm in Neural Estrogen Receptors and Its Possible Behavioral Consequences

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Synchronizing Effect of Photoperiodicity on Ovulation in Hamsters1

Cited by 39 publications

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Circadian organization of the estrous cycle of the golden hamster.

Circadian organization of the estrous cycle of the golden hamster.

Influence of Photoperiod on Reproductive Development in the Golden Hamster

Characterization of a Pineal-Independent Diurnal Rhythm in Neural Estrogen Receptors and Its Possible Behavioral Consequences

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Synchronizing Effect of Photoperiodicity on Ovulation in Hamsters¹