Circadian Locomotor Activity Rhythms in the African Clawed Frog, Xenopus laevis: The Role of the Eye and the Hypothalamus

Harada, Yasuhiro; Goto, Maki; Ebihara, Shigemitsu; Fujisawa, Hajime; Kegasawa, Kazuo; Oishi, Tadashi

doi:10.1076/brhm.29.1.30.3043

Cited by 9 publications

(3 citation statements)

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“…For example, the circadian locomotor activity rhythm of Xenopus laevis is lost by lesion of the hypothalamus including the SCN (35). Also, the neural connections of the hypothalamus to the retina have been reported neuroanatomically in Rana esculenta (36).…”

Section: Resultsmentioning

confidence: 98%

Circadian Activation of Bullfrog Retinal Mitogen-activated Protein Kinase Associates with Oscillator Function

Harada

Sanada

Fukada

2000

Journal of Biological Chemistry

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The vertebrate retina retains a circadian oscillator, and its oscillation is self-sustained with a period close to 24 h under constant environmental conditions. Here we show that bullfrog retinal mitogen-activated protein kinase (MAPK) exhibits an in vivo circadian rhythm in phosphorylation with a peak at night in a light/dark cycle. The phosphorylation rhythm of MAPK persists in constant darkness with a peak at subjective night, and this self-sustained rhythm is also observed in cultured retinas, indicating its close interaction with the retinal oscillator. The rhythmically phosphorylated MAPK is detected only in a discrete subset of amacrine cells despite ubiquitous distribution of MAPK throughout the retinal layers. Treatment of the cultured retinas with MAPK kinase (MEK) inhibitor PD98059 suppresses MAPK phosphorylation during the subjective night, and this pulse perturbation of MEK activity induces a significant phase delay (4 -8 h) of the retinal circadian rhythm in MAPK and MEK phosphorylation. These observations strongly suggest that the site-specific and time-of-dayspecific activation of MAPK contributes to the circadian time-keeping mechanism of the retinal clock system.The physiology and behavior of living organisms from bacteria to humans show daily fluctuations with a period of approximately 24 h, and the oscillations controlled by autonomous circadian oscillators are termed circadian rhythms (1, 2). These rhythms can be synchronized (entrained) to environmental time cues such as light or temperature but are sustained under constant environmental conditions in the absence of time cues (1). A lot of studies on the Drosophila melanogaster clock system have demonstrated that a transcription/translation-based feedback loop is involved in generating the circadian rhythmicity (2, 3). In Drosophila, a complex of two transcription factors, dCLOCK and CYCLE (dBMAL1), positively regulates both period (per) and timeless (tim) transcription through CACGTG E-box elements found in their promoters (4 -6), leading to an increase in protein levels of both PER and TIM. PER and TIM proteins form a heterodimer and translocate to the nucleus where PER/TIM negatively regulate dCLOCK/CYCLE-induced transcription of their own promoters (5, 7-11). Thus, these positive and negative elements constitute an autoregulatory feedback loop.In vertebrates, autonomous circadian oscillators are located in several neuronal tissues such as the retina, pineal gland, and suprachiasmatic nucleus (SCN) 1 (1, 12-17). Homologs of per, clock, and bmal1 have been identified in vertebrates, and they are expressed in SCN of mammals (reviewed in Refs. 2 and 18). It is now postulated that the molecular framework of the circadian oscillator is conserved from flies to mammals, although each clock component appears to function in a slightly different manner (reviewed in Refs. 19 and 20).In addition to the transcriptional and translational regulation, post-translational modifications of clock gene products play important roles in the clock system. Droso...

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Section: Resultsmentioning

confidence: 98%

Circadian Activation of Bullfrog Retinal Mitogen-activated Protein Kinase Associates with Oscillator Function

Harada

Sanada

Fukada

2000

Journal of Biological Chemistry

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“…Despite the plausibility of independent pacemaking activity of a retinal clock as demonstrated in Japanese quail, this does not seem to be the case in the retina of either the X. laevis or mice. In X. laevis , for example, blinding does not affect circadian activity rhythms (Harada et al, 1998). Furthermore, melatonin synthesis by photoreceptors is locally limited because it is rapidly degraded to 5-methoxytryamine (Cahill and Besharse, 1989), and its synthesis is rate limited in capacity at the first enzymatic step, tryptophan hydroxylase (Cahill and Besharse, 1990).…”

Section: Relationship Of the Retinal Clock To The Scn Pacemakermentioning

confidence: 99%

The Retina and Other Light-sensitive Ocular Clocks

Besharse

McMahon

2016

J Biol Rhythms

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Ocular clocks, first identified in the retina, are also found in the retinal pigment epithelium (RPE), cornea and ciliary body. The retina is a complex tissue of many cell types and considerable effort has gone into determining which cell types exhibit clock properties. Current data suggest that photoreceptors as well as inner retinal neurons exhibit clock properties with photoreceptors dominating in non-mammalian vertebrates and inner retinal neurons dominating in mice. However, these differences may in part reflect the choice of circadian output, and it is likely that clock properties are widely dispersed among many retinal cell types. The phase of the retinal clock can be set directly by light. In non-mammalian vertebrates direct light sensitivity is commonplace among body clocks, but in mice only the retina and cornea retain direct light-dependent phase regulation. This distinguishes the retina and possibly other ocular clocks from peripheral oscillators whose phase depends on the pace-making properties of the hypothalamic central brain clock, the suprachiasmatic nuclei (SCN). However, in mice retinal circadian oscillations dampen quickly in isolation due to weak coupling of its individual cell autonomous oscillators and there is no evidence that retinal clocks are directly controlled through input from other oscillators. Retinal circadian regulation in both mammals and non-mammalian vertebrates uses melatonin and dopamine as dark- and light-adaptive neuromodulators respectively, and light can regulate circadian phase indirectly through dopamine signaling. The melatonin/dopamine system appears to have evolved among non-mammalian vertebrates and retained with modification in mammals. Circadian clocks in the eye are critical for optimum visual function where they play a role fine tuning visual sensitivity, and their disruption can impact diseases such as glaucoma or retinal degeneration syndromes.

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“…Circadian systems composed of multiple autonomous circadian oscillators that regulate diverse outputs within the same organism have been described in birds (Cassone and Menaker, 1984), reptiles (Underwood, 1977(Underwood, , 1981(Underwood, , 1983Tosini and Menaker, 1998), amphibians (Harada et al, 1998), and mammals (Tosini and Menaker, 1996a). Understanding the organization of such systems, specifically how the component oscillators interact to produce a coordinated adaptive temporal structure, is a major problem in circadian biology.…”

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confidence: 99%

Circadian Rhythm of ERG inIguana iguana: Role of the Pineal

Miranda‐Anaya¹,

Bartell²,

Yamazaki³

et al. 2000

J Biol Rhythms

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In green iguanas, the pineal controls the circadian rhythm of body temperature but not the rhythm of locomotor activity. As part of a program to investigate the characteristics of this multioscillator circadian system, the authors studied the circadian rhythms of the electroretinographic response (ERG) and asked whether the pineal gland is necessary for the expression of this rhythm. ERGs from a total of 24 anesthetized juvenile iguanas were recorded under four different conditions: (a) complete darkness (DD), (b) dim light-dark cycles (dLD), (c) constant dim light (dLL), and (d) pinealectomized in DD. Results demonstrate that the b-wave component of the ERG shows a very clear circadian rhythm in DD and that this rhythm persists in dLL and entrains to dLD cycles. The ERG response is maximally sensitive during the subjective day. Pinealectomy does not abolish the circadian rhythm in ERG, demonstrating that the oscillator responsible for the ERG rhythm is located elsewhere.

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Circadian Locomotor Activity Rhythms in the African Clawed Frog, Xenopus laevis: The Role of the Eye and the Hypothalamus

Cited by 9 publications

References 0 publications

Circadian Activation of Bullfrog Retinal Mitogen-activated Protein Kinase Associates with Oscillator Function

Circadian Activation of Bullfrog Retinal Mitogen-activated Protein Kinase Associates with Oscillator Function

The Retina and Other Light-sensitive Ocular Clocks

Circadian Rhythm of ERG inIguana iguana: Role of the Pineal

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