A 24-HOUR PERIODICITY IN THE “LH-RELEASE APPARATUS” OF FEMALE RATS, DISCLOSED BY BARBITURATE SEDATION<sup>1</sup>

Everett, John W.; Sawyer, Charles H.

doi:10.1210/endo-47-3-198

Cited by 600 publications

(285 citation statements)

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“…The involvement of a daily neural signal required for ovulation was first indicated by classic studies in which barbiturate treatment of rats in the midafternoon of proestrus delayed ovulation by 24 h but had no effect when administered at other times (13), indicating that there is a ''critical period'' during which this signal is conveyed and after which ovulation becomes inevitable. The time of the critical period for daily neural signal transmission in mice is unknown.…”

Section: Discussionmentioning

confidence: 99%

Diurnal and estradiol-dependent changes in gonadotropin-releasing hormone neuron firing activity

Christian

Mobley

Moenter

2005

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

192

213

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A robust gonadotropin-releasing hormone (GnRH) surge is a prerequisite signal for the luteinizing hormone (LH) surge that triggers ovulation. In rodents, the GnRH surge is initiated by elevated estradiol and a diurnal switch in estrogen action from negative to positive feedback. The ability of constant estradiol treatment to induce daily LH surges was tested in adult mice that were ovariectomized (OVX) or OVX and treated with estradiol implants (OVX؉E). LH in OVX mice showed no time-of-day difference. In contrast, OVX؉E mice showed a large LH surge (8-to 124-fold relative to the a.m.) in p.m. samples on d 2-5 post-OVX؉E. Targeted extracellular recordings were used to examine changes in firing activity of GnRH neurons in brain slices. There was no time-of-day difference in cells from OVX mice. In contrast, OVX؉E cells recorded in the p.m. showed an increased mean firing rate and instantaneous firing frequency, which could increase GnRH release, and decreased duration of quiescence between bouts of firing, possibly reflecting increased pulse frequency, compared with cells recorded in the a.m. In the a.m., OVX؉E cells showed changes in GnRH neuron firing reflecting negative feedback compared with OVX cells, whereas in the p.m., OVX؉E cells exhibited changes suggesting positive feedback. These data indicate that differences in pattern and level of individual GnRH neuron firing may reflect the switch in estradiol action and underlie GnRH surge generation. The persistence of altered GnRH neuron activity in slices indicates that this approach can be used to study the neurobiological mechanisms of surge generation.luteinizing hormone ͉ mouse model ͉ surge ͉ electrophysiology ͉ neuroendocrinology

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Section: Discussionmentioning

confidence: 99%

Diurnal and estradiol-dependent changes in gonadotropin-releasing hormone neuron firing activity

Christian

Mobley

Moenter

2005

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

192

213

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“…The importance of circadian (about a day) timing in hormone production/secretion has been known since the 1950s when Everett and Sawyer determined that a stimulatory signal occurring during a narrow temporal window on the afternoon of proestrus is necessary for induction of ovulation later that night (Everett and Sawyer, 1950). Such close temporal organization is important for successful reproduction, as numerous hormone-dependent behavioral and physiological processes must be coordinated.…”

Section: Circadian Aspects Of Reproductionmentioning

confidence: 99%

The regulation of neuroendocrine function: Timing is everything

Kriegsfeld

Silver

2006

Hormones and Behavior

129

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Hormone secretion is highly organized temporally, achieving optimal biological functioning and health. The master clock located in the suprachiasmatic nucleus (SCN) of the hypothalamus coordinates the timing of circadian rhythms, including daily control of hormone secretion. In the brain, the SCN drives hormone secretion. In some instances, SCN neurons make direct synaptic connections with neurosecretory neurons. In other instances, SCN signals set the phase of "clock genes" that regulate circadian function at the cellular level within neurosecretory cells. The protein products of these clock genes can also exert direct transcriptional control over neuroendocrine releasing factors. Clock genes and proteins are also expressed in peripheral endocrine organs providing additional modes of temporal control. Finally, the SCN signals endocrine glands via the autonomic nervous system, allowing for rapid regulation via multisynaptic pathways. Thus, the circadian system achieves temporal regulation of endocrine function by a combination of genetic, cellular, and neural regulatory mechanisms to ensure that each response occurs in its correct temporal niche. The availability of tools to assess the phase of molecular/cellular clocks and of powerful tract tracing methods to assess connections between "clock cells" and their targets provides an opportunity to examine circadian-controlled aspects of neurosecretion, in the search for general principles by which the endocrine system is organized. KeywordsCircadian; Diurnal; Endocrinel; Neurosecretion; Clock genes; Suprachiasmatic Circadian aspects of reproductionThe importance of circadian (about a day) timing in hormone production/secretion has been known since the 1950s when Everett and Sawyer determined that a stimulatory signal occurring during a narrow temporal window on the afternoon of proestrus is necessary for induction of ovulation later that night (Everett and Sawyer, 1950). Such close temporal organization is important for successful reproduction, as numerous hormone-dependent behavioral and physiological processes must be coordinated. If optimal temporal relationships are disrupted, pronounced deficits in fertility can result. For example, ovulation, behavioral estrus, fertilization, and pregnancy maintenance require a specific

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“…The administration of pentobarbitone sodium on the afternoon of pro-oestrus blocks the preovulatory surge of gonadotrophins and ovulation is prevented (Everett & Sawyer, 1950;Naftolin, Brown-Grant & Corker, 1972;Ayalon, Tsafriri, Lindner, Cordova & Harell, 1972;Butcher, Collins & Fugo, 1974;Ashiru & Blake, 1978). Daily administration of the drug, starting on the day of pro-oestrus, results in atresia of Graafian follicles within 3 days (Everett & Sawyer, 1950).…”

Section: Introductionmentioning

confidence: 99%

Follicles explanted from pentobarbitone-treated rats provide a model for atresia

Braw¹,

Tsafriri²

1980

Reproduction

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A 24-HOUR PERIODICITY IN THE “LH-RELEASE APPARATUS” OF FEMALE RATS, DISCLOSED BY BARBITURATE SEDATION¹

Cited by 600 publications

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Diurnal and estradiol-dependent changes in gonadotropin-releasing hormone neuron firing activity

Diurnal and estradiol-dependent changes in gonadotropin-releasing hormone neuron firing activity

The regulation of neuroendocrine function: Timing is everything

Follicles explanted from pentobarbitone-treated rats provide a model for atresia

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A 24-HOUR PERIODICITY IN THE “LH-RELEASE APPARATUS” OF FEMALE RATS, DISCLOSED BY BARBITURATE SEDATION1

Cited by 600 publications

References 0 publications

Diurnal and estradiol-dependent changes in gonadotropin-releasing hormone neuron firing activity

Diurnal and estradiol-dependent changes in gonadotropin-releasing hormone neuron firing activity

The regulation of neuroendocrine function: Timing is everything

Follicles explanted from pentobarbitone-treated rats provide a model for atresia

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A 24-HOUR PERIODICITY IN THE “LH-RELEASE APPARATUS” OF FEMALE RATS, DISCLOSED BY BARBITURATE SEDATION¹