Circadian Rhythms in the Neuronal Network Timing the Luteinizing Hormone Surge

Endocrinology ◽  
2021 ◽  
Author(s):  
Karen J Tonsfeldt ◽  
Pamela L Mellon ◽  
Hanne M Hoffmann
Keyword(s):  
Circadian Rhythms ◽  
Luteinizing Hormone ◽  
Reproductive Function ◽  
Day Length ◽  
Molecular Clocks ◽  
Biological Clocks ◽  
Environmental Light ◽  
Luteinizing Hormone Surge ◽  
Life On Earth ◽  
Temporal Rhythm

Abstract For 3.5 billion years before electric light was invented in 1879, life on Earth evolved under the pattern of light during the day and darkness during the night. Through evolution, nearly all organisms internalized the temporal rhythm of Earth’s 24-hour rotation and evolved self-sustaining biological clocks with a ~24-hour rhythm. These internal rhythms are called circadian rhythms, and the molecular constituents that generate them are called molecular circadian clocks. Alignment of molecular clocks with the environmental light-dark rhythms optimizes physiology and behavior. This is particularly true for reproductive function, in which seasonal breeders use day-length information to time yearly changes in fertility. However, it is becoming increasingly clear that light-induced disruption of circadian rhythms can negatively impact fertility in non-seasonal breeders as well. In particular, the luteinizing hormone surge promoting ovulation, is sensitive to circadian disruption. In this review, we will summarize our current understanding of the neuronal networks that underlie circadian rhythms and the luteinizing hormone surge.

scholarly journals Melatonin, Clock Genes, and Mammalian Reproduction: What Is the Link?

2021 ◽  
Vol 22 (24) ◽  
pp. 13240
Author(s):  
Amnon Brzezinski ◽  
Seema Rai ◽  
Adyasha Purohit ◽  
Seithikurippu R. Pandi-Perumal
Keyword(s):  
Circadian Rhythm ◽  
Circadian Rhythms ◽  
Molecular Clock ◽  
Reproductive Performance ◽  
Clock Genes ◽  
Current Knowledge ◽  
Reproductive Function ◽  
The Body ◽  
Molecular Clocks ◽  
Biological Regulation

Physiological processes and behaviors in many mammals are rhythmic. Recently there has been increasing interest in the role of circadian rhythmicity in the control of reproductive function. The circadian rhythm of the pineal hormone melatonin plays a role in synchronizing the reproductive responses of animals to environmental light conditions. There is some evidence that melatonin may have a role in the biological regulation of circadian rhythms and reproduction in humans. Moreover, circadian rhythms and clock genes appear to be involved in optimal reproductive performance. These rhythms are controlled by an endogenous molecular clock within the suprachiasmatic nucleus (SCN) in the hypothalamus, which is entrained by the light/dark cycle. The SCN synchronizes multiple subsidiary oscillators (clock genes) existing in various tissues throughout the body. The basis for maintaining the circadian rhythm is a molecular clock consisting of transcriptional/translational feedback loops. Circadian rhythms and clock genes appear to be involved in optimal reproductive performance. This mini review summarizes the current knowledge regarding the interrelationships between melatonin and the endogenous molecular clocks and their involvement in reproductive physiology (e.g., ovulation) and pathophysiology (e.g., polycystic ovarian syndrome).

Twilight and day length affects the seasonality of entrainment and endogenous circadian rhythms in a fish, Couesius plumbeus

1981 ◽  
Vol 59 (7) ◽  
pp. 1326-1334 ◽  
Author(s):  
Martin Kavaliers ◽  
Donald M. Ross
Keyword(s):  
Circadian Rhythms ◽  
Seasonal Changes ◽  
Phase Relationship ◽  
Day Length ◽  
Constant Darkness ◽  
Diurnal Activity ◽  
Circadian Period ◽  
Dark Cycle ◽  
Environmental Light ◽  
Couesius Plumbeus

Twilight and day-length portions of the light-dark cycle determine the seasonal course of (i) the phase relationship (ψ) between activity and the daily environmental light–dark cycle, (ii) the duration of activity (α), and (iii) the circadian period (τ) under constant darkness of the lake chub (Couesius plumbeus). With fish held under seasonally appropriate light–dark cycles with twilight (LD + t), the onset of diurnal activity occurred during dawn and its timing (ψonset) followed a bimodal annual pattern that was correlated with seasonal changes in the duration and physical characteristics of twilight. The end of activity occurred during dusk (ψoffset) and followed a unimodal annual pattern that was determined by day length. α followed a sigmoidal annual pattern under LD + t. The circadian period underwent significant seasonal changes with maximum and minimum τ values occurring during summer and winter, respectively. Fish that were entrained to rectangular light–dark cycles that excluded twilights (LD) failed to show any seasonal changes in ψ and τ and the sigmoidal relation between α and day length was absent.

scholarly journals Targeted mutation of secretogranin-2 disrupts sexual behavior and reproduction in zebrafish

2020 ◽  
Vol 117 (23) ◽  
pp. 12772-12783 ◽  
Author(s):  
Kimberly Mitchell ◽  
Wo Su Zhang ◽  
Chunyu Lu ◽  
Binbin Tao ◽  
Lu Chen ◽  
...  
Keyword(s):  
Sexual Behavior ◽  
Luteinizing Hormone ◽  
Large Scale ◽  
Reproductive Function ◽  
Hormone Release ◽  
Wild Type ◽  
Targeted Mutation ◽  
Luteinizing Hormone Surge ◽  
Courtship Behaviors ◽  
Spawning Success

The luteinizing hormone surge is essential for fertility as it triggers ovulation in females and sperm release in males. We previously reported that secretoneurin-a, a neuropeptide derived from the processing of secretogranin-2a (Scg2a), stimulates luteinizing hormone release, suggesting a role in reproduction. Here we provide evidence that mutation of thescg2aandscg2bgenes using TALENs in zebrafish reduces sexual behavior, ovulation, oviposition, and fertility. Large-scale spawning within-line crossings (n= 82 to 101) were conducted. Wild-type (WT) males paired with WT females successfully spawned in 62% of the breeding trials. Spawning success was reduced to 37% (P= 0.006), 44% (P= 0.0169), and 6% (P< 0.0001) forscg2a−/−,scg2b−/−, andscg2a−/−;scg2b−/−mutants, respectively. Comprehensive video analysis indicates thatscg2a−/−;scg2b−/−mutation reduces all male courtship behaviors. Spawning success was 47% in saline-injected WT controls compared to 11% in saline-injectedscg2a−/−;scg2b−/−double mutants. For these mutants, spawning success increased 3-fold following a single intraperitoneal (i.p.) injection of synthetic secretoneurin-a (P= 0.0403) and increased 3.5-fold with injection of human chorionic gonadotropin (hCG). Embryonic survival at 24 h remained on average lower inscg2a−/−;scg2b−/−fish compared to WT injected with secretoneurin-a (P< 0.001). Significant reductions in the expression of gonadotropin-releasing hormone 3 in the hypothalamus, and luteinizing hormone beta and glycoprotein alpha subunits in the pituitary provide evidence for disrupted hypothalamo-pituitary function inscg2aandscg2bmutant fish. Our results indicate that secretogranin-2 is required for optimal reproductive function and support the hypothesis that secretoneurin is a reproductive hormone.

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