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Grunst ML, Grunst AS. Endocrine effects of exposure to artificial light at night: A review and synthesis of knowledge gaps. Mol Cell Endocrinol 2023; 568-569:111927. [PMID: 37019171 DOI: 10.1016/j.mce.2023.111927] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Revised: 03/26/2023] [Accepted: 03/29/2023] [Indexed: 04/07/2023]
Abstract
Animals have evolved with natural patterns of light and darkness, such that light serves as an important zeitgeber, allowing adaptive synchronization of behavior and physiology to external conditions. Exposure to artificial light at night (ALAN) interferes with this process, resulting in dysregulation of endocrine systems. In this review, we evaluate the endocrine effects of ALAN exposure in birds and reptiles, identify major knowledge gaps, and highlight areas for future research. There is strong evidence for ecologically relevant levels of ALAN acting as an environmental endocrine disruptor. However, most studies focus on the pineal hormone melatonin, corticosterone release via the hypothalamus-pituitary-adrenal axis, or regulation of reproductive hormones via the hypothalamus-pituitary-gonadal axis, leaving effects on other endocrine systems largely unknown. We call for more research spanning a diversity of hormonal systems and levels of endocrine regulation (e.g. circulating hormone levels, receptor numbers, strength of negative feedback), and investigating involvement of molecular mechanisms, such as clock genes, in hormonal responses. In addition, longer-term studies are needed to elucidate potentially distinct effects arising from chronic exposure. Other important areas for future research effort include investigating intraspecific and interspecific variability in sensitivity to light exposure, further distinguishing between distinct effects of different types of light sources, and assessing impacts of ALAN exposure early in life, when endocrine systems remain sensitive to developmental programming. The effects of ALAN on endocrine systems are likely to have a plethora of downstream effects, with implications for individual fitness, population persistence, and community dynamics, especially within urban and suburban environments.
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Affiliation(s)
- Melissa L Grunst
- Littoral, Environnement et Sociétés (LIENS), UMR 7266 CNRS-La Rochelle Université, 2 Rue Olympe de Gouges, FR-17000, La Rochelle, France.
| | - Andrea S Grunst
- Littoral, Environnement et Sociétés (LIENS), UMR 7266 CNRS-La Rochelle Université, 2 Rue Olympe de Gouges, FR-17000, La Rochelle, France
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2
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Abstract
Artificial light at night (ALAN) is increasing exponentially worldwide, accelerated by the transition to new efficient lighting technologies. However, ALAN and resulting light pollution can cause unintended physiological consequences. In vertebrates, production of melatonin—the “hormone of darkness” and a key player in circadian regulation—can be suppressed by ALAN. In this paper, we provide an overview of research on melatonin and ALAN in vertebrates. We discuss how ALAN disrupts natural photic environments, its effect on melatonin and circadian rhythms, and different photoreceptor systems across vertebrate taxa. We then present the results of a systematic review in which we identified studies on melatonin under typical light-polluted conditions in fishes, amphibians, reptiles, birds, and mammals, including humans. Melatonin is suppressed by extremely low light intensities in many vertebrates, ranging from 0.01–0.03 lx for fishes and rodents to 6 lx for sensitive humans. Even lower, wavelength-dependent intensities are implied by some studies and require rigorous testing in ecological contexts. In many studies, melatonin suppression occurs at the minimum light levels tested, and, in better-studied groups, melatonin suppression is reported to occur at lower light levels. We identify major research gaps and conclude that, for most groups, crucial information is lacking. No studies were identified for amphibians and reptiles and long-term impacts of low-level ALAN exposure are unknown. Given the high sensitivity of vertebrate melatonin production to ALAN and the paucity of available information, it is crucial to research impacts of ALAN further in order to inform effective mitigation strategies for human health and the wellbeing and fitness of vertebrates in natural ecosystems.
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3
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Ouyang JQ, Davies S, Dominoni D. Hormonally mediated effects of artificial light at night on behavior and fitness: linking endocrine mechanisms with function. ACTA ACUST UNITED AC 2018; 221:221/6/jeb156893. [PMID: 29545373 DOI: 10.1242/jeb.156893] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Alternation between day and night is a predictable environmental fluctuation that organisms use to time their activities. Since the invention of artificial lighting, this predictability has been disrupted and continues to change in a unidirectional fashion with increasing urbanization. As hormones mediate individual responses to changing environments, endocrine systems might be one of the first systems affected, as well as being the first line of defense to ameliorate any negative health impacts. In this Review, we first highlight how light can influence endocrine function in vertebrates. We then focus on four endocrine axes that might be affected by artificial light at night (ALAN): pineal, reproductive, adrenal and thyroid. Throughout, we highlight key findings, rather than performing an exhaustive review, in order to emphasize knowledge gaps that are hindering progress on proposing impactful and concrete plans to ameliorate the negative effects of ALAN. We discuss these findings with respect to impacts on human and animal health, with a focus on the consequences of anthropogenic modification of the night-time environment for non-human organisms. Lastly, we stress the need for the integration of field and lab experiments as well as the need for long-term integrative eco-physiological studies in the rapidly expanding field of light pollution.
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Affiliation(s)
- Jenny Q Ouyang
- Department of Biology, University of Nevada, Reno, Reno, NV 89557, USA
| | - Scott Davies
- Department of Biology, University of Nevada, Reno, Reno, NV 89557, USA.,Department of Biological Sciences, Quinnipiac University, Hamden, CT 06518, USA
| | - Davide Dominoni
- Department of Animal Ecology, Netherlands Institute of Ecology (NIOO-KNAW), 6708 Wageningen, The Netherlands.,Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow G12 8QQ, UK
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4
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Crews D, Hingorani V, Nelson RJ. Role of the Pineal Gland in the Control of Annual Reproductive Behavioral and Physiological Cycles in the Red-Sided Garter Snake (Thamnophis sirtalis parietalis). J Biol Rhythms 2016. [DOI: 10.1177/074873048800300307] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Red-sided garter snakes (Thamnophis sirtalis parietalis) exhibit a dissociated re productive pattern in nature: Male snakes court and mate with females after emergence from hibernation, when the gonads are regressed and not producing gametes or sex steroid hor mones. The proximate environmental cues used for timing this behavior appear to be the onset of warm ambient temperatures after prolonged exposure to cold temperatures. Pinealectomy blocks the normal onset of vernal courtship behavior in red-sided garter snakes. In the present study, snakes captured in the spring or the fall were pinealectomized in different seasons (i.e., spring or fall) prior to the onset of hibernation. Upon emergence, only 1 of 36 sham-operated animals failed to exhibit courtship behavior; 4 of 29 pinealectomized animals exhibited some courtship behavior, but none reached criterion. No animals courted 18 weeks after emer gence, and plasma testosterone levels were similar in pinealectomized and sham-operated animals, indicating that pinealectomy did not simply rephase courtship behavior in these snakes. Although some animals lost mass while others gained mass over the course of the study, this variable does not account for the absence of mating behavior in pinealectomized garter snakes. These data lend additional support to the hypothesis that the pineal gland directly influences reproductive behavior in the red-sided garter snake.
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Affiliation(s)
- David Crews
- Institute of Reproductive Biology, Department of Zoology, University of Texas, Austin, Texas 78712-1064
| | - Vinita Hingorani
- Institute of Reproductive Biology, Department of Zoology, University of Texas, Austin, Texas 78712-1064
| | - Randy J. Nelson
- Departments of Psychology and Population Dynamics, The Johns Hopkins University, Baltimore, Maryland 21218
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Malik S, Singh J, Trivedi AK, Singh S, Rani S, Kumar V. Nocturnal melatonin levels decode daily light environment and reflect seasonal states in night-migratory blackheaded bunting (Emberiza melanocephala). Photochem Photobiol Sci 2015; 14:963-71. [DOI: 10.1039/c5pp00045a] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We proposed two perhaps overlapping hypotheses.
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Affiliation(s)
- Shalie Malik
- Department of Zoology
- University of Lucknow
- DST-IRHPA Center for Excellence in Biological Rhythm Research
- Lucknow 226 007
- India
| | - Jyoti Singh
- Department of Zoology
- University of Delhi
- DST-IRHPA Center for Excellence in Biological Rhythm Research
- Delhi 110 007
- India
| | | | - Sudhi Singh
- Department of Zoology
- N.S.N. (P.G.) College
- Lucknow, 226 001
- India
| | - Sangeeta Rani
- Department of Zoology
- University of Lucknow
- DST-IRHPA Center for Excellence in Biological Rhythm Research
- Lucknow 226 007
- India
| | - Vinod Kumar
- Department of Zoology
- University of Delhi
- DST-IRHPA Center for Excellence in Biological Rhythm Research
- Delhi 110 007
- India
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6
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Moore AF, Menaker M. The effect of light on melatonin secretion in the cultured pineal glands of Anolis lizards. Comp Biochem Physiol A Mol Integr Physiol 2011; 160:301-8. [DOI: 10.1016/j.cbpa.2011.06.027] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2011] [Revised: 06/28/2011] [Accepted: 06/29/2011] [Indexed: 11/30/2022]
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7
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Krohmer R, Lutterschmidt D. Environmental and Neuroendorcrine Control of Reproduction in Snakes. REPRODUCTIVE BIOLOGY AND PHYLOGENY OF SNAKES 2011. [DOI: 10.1201/b10879-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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8
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Physiology and pharmacology of melatonin in relation to biological rhythms. Pharmacol Rep 2009; 61:383-410. [PMID: 19605939 DOI: 10.1016/s1734-1140(09)70081-7] [Citation(s) in RCA: 198] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2008] [Revised: 05/01/2009] [Indexed: 01/01/2023]
Abstract
Melatonin is an evolutionarily conserved molecule that serves a time-keeping function in various species. In vertebrates, melatonin is produced predominantly by the pineal gland with a marked circadian rhythm that is governed by the central circadian pacemaker (biological clock) in the suprachiasmatic nuclei of the hypothalamus. High levels of melatonin are normally found at night, and low levels are seen during daylight hours. As a consequence, melatonin has been called the "darkness hormone". This review surveys the current state of knowledge regarding the regulation of melatonin synthesis, receptor expression, and function. In particular, it addresses the physiological, pathological, and therapeutic aspects of melatonin in humans, with an emphasis on biological rhythms.
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Lutterschmidt DI, Mason RT. Endocrine mechanisms mediating temperature-induced reproductive behavior in red-sided garter snakes (Thamnophis sirtalis parietalis). J Exp Biol 2009; 212:3108-18. [DOI: 10.1242/jeb.033100] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
SUMMARY
We investigated the mechanisms by which temperature induces seasonal reproductive behavior in red-sided garter snakes (Thamnophis sirtalis parietalis). Specifically, we addressed whether elevated temperatures during winter dormancy influence (1) diel melatonin and corticosterone rhythms; (2) sex steroid hormone and corticosterone profiles; and (3) the expression of reproductive behavior following emergence. Elevated hibernation temperatures (i.e. 10°C versus 5°C) significantly increased overall melatonin and decreased corticosterone concentrations of snakes. The temperature-induced differences in melatonin rhythms between the 5°C and 10°C treatment groups persisted even after both groups were again acclimated to 10°C, indicating that cold temperature exposure has a lasting influence on melatonin rhythms. Elevated hibernation temperatures also significantly altered androgen and corticosterone profiles of snakes,providing a potential mechanism to explain reported annual variation in steroid hormones. Although previous studies indicate that male red-sided garter snakes exhibit a dissociated reproductive strategy, we demonstrate the presence of intersexual variation in sex steroid hormone profiles, as estradiol concentrations of female snakes increased significantly prior to spring mating activity. Importantly, the percentage change in body mass did not differ significantly between snakes in the hibernation treatments,indicating that the observed changes in hormone profiles are indeed temperature induced and not simply an indirect result of significant changes in the energy balance of snakes. Finally, in males maintained at 10°C during winter dormancy the onset of courtship behavior following emergence was delayed. Our results suggest that environmental temperatures induce reproductive behavior, in part, via changes in diel melatonin and/or corticosterone rhythms in this seasonally breeding reptile.
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Affiliation(s)
| | - Robert T. Mason
- Department of Zoology, Oregon State University, Corvallis, OR 97331,USA
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10
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Bagnaresi P, Alves E, Borges da Silva H, Epiphanio S, Mota MM, Garcia CR. Unlike the synchronous Plasmodium falciparum and P. chabaudi infection, the P. berghei and P. yoelii asynchronous infections are not affected by melatonin. Int J Gen Med 2009; 2:47-55. [PMID: 20360886 PMCID: PMC2840578 DOI: 10.2147/ijgm.s3699] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
We have previously reported that Plasmodium chabaudi and P.
falciparum sense the hormone melatonin and this could be responsible for
the synchrony of malaria infection. In P. chabaudi and P.
falciparum, melatonin induces calcium release from internal stores, and
this response is abolished by U73122, a phospholipase C inhibitor, and luzindole, a
melatonin-receptor competitive antagonist. Here we show that, in
vitro, melatonin is not able to modulate cell cycle, nor to elicit an
elevation in intracellular calcium concentration of the intraerythrocytic forms of
P. berghei or P. yoelii, two rodent parasites
that show an asynchrononous development in vivo. Interestingly,
melatonin and its receptor do not seem to play a role during hepatic infection by
P. berghei sporozoites either. These data strengthen the
hypothesis that host-derived melatonin does not synchronize malaria infection caused
by P. berghei and P. yoelii. Moreover, these data
explain why infections by these parasites are asynchronous, contrary to what is
observed in P. falciparum and P. chabaudi
infections.
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Affiliation(s)
- Piero Bagnaresi
- Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo, São Paulo, Brazil
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11
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Paul MJ, Zucker I, Schwartz WJ. Tracking the seasons: the internal calendars of vertebrates. Philos Trans R Soc Lond B Biol Sci 2008; 363:341-61. [PMID: 17686736 PMCID: PMC2606754 DOI: 10.1098/rstb.2007.2143] [Citation(s) in RCA: 155] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Animals have evolved many season-specific behavioural and physiological adaptations that allow them to both cope with and exploit the cyclic annual environment. Two classes of endogenous annual timekeeping mechanisms enable animals to track, anticipate and prepare for the seasons: a timer that measures an interval of several months and a clock that oscillates with a period of approximately a year. Here, we discuss the basic properties and biological substrates of these timekeeping mechanisms, as well as their reliance on, and encoding of environmental cues to accurately time seasonal events. While the separate classification of interval timers and circannual clocks has elucidated important differences in their underlying properties, comparative physiological investigations, especially those regarding seasonal prolactin secretions, hint at the possibility of common substrates.
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Affiliation(s)
- Matthew J Paul
- Department of Neurology, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester, MA 01655, USA.
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12
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Firth BT, Belan I, Kennaway DJ. Persistence of a plasma melatonin rhythm in constant darkness and its inhibition by constant light in the sleepy lizard, Tiliqua rugosa. J Pineal Res 2006; 41:15-20. [PMID: 16842536 DOI: 10.1111/j.1600-079x.2006.00322.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
This study determined whether a blood plasma melatonin rhythm persists in constant photothermal environments in the sleepy lizard, Tiliqua rugosa. It builds upon an earlier investigation which provided equivocal results as to whether an in vivo melatonin rhythm persists in constant dark (DD) and light (LL) and temperature in this species. Using more frequent sampling points and new assay techniques, the present study showed that the melatonin rhythm persisted for at least 6 days at temperatures of 25 and 33 degrees C in constant dark (DD). The melatonin rhythm, however, was largely eliminated in constant light (LL) at 33 degrees C, thereby contradicting some previous findings in other species of reptiles where melatonin levels were apparently insensitive to an unexpected pulse of light at night. These results demonstrate that the sleepy lizard has a persistent, possibly circadian rhythm of melatonin in DD and constant temperature, and that the rhythm is inhibited by LL and constant temperature. Therefore, the sleepy lizard pineal gland may be an independent oscillator capable of driving the melatonin rhythm and be a transducer of the seasonally changing external photothermal environment.
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Affiliation(s)
- Bruce T Firth
- Department of Anatomical Sciences, University of Adelaide, Adelaide, Australia.
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13
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Ceinos RM, Rábade S, Soengas JL, Míguez JM. Indoleamines and 5-methoxyindoles in trout pineal organ in vivo: daily changes and influence of photoperiod. Gen Comp Endocrinol 2005; 144:67-77. [PMID: 15950974 DOI: 10.1016/j.ygcen.2005.04.010] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/28/2004] [Revised: 04/15/2005] [Accepted: 04/25/2005] [Indexed: 10/25/2022]
Abstract
This study describes the diel rhythms in several indoleamines, melatonin, and related 5-methoxyindoles in the pineal organ of rainbow trout in vivo. In addition, the effect of different photoperiod conditions was evaluated. Melatonin levels displayed clear daily rhythms in the pineal organ of rainbow trout kept experimentally under long (LD 16:08), neutral (LD 12:12), and short (LD 08:16) photoperiods. Duration of melatonin signal was dependent on the night length of prevailing photoperiod, while peak amplitude was higher when lengthening the photoperiod. Significant daily rhythms in 5-HT content, the precursor of melatonin synthesis, were found in neutral and short photoperiod with increases of the amine content just after the light-dark interphase and decreases in the middle of the night, which were more important under short photoperiod. In contrast, no significant 24-h cyclic variation was found in pineal 5-HT content under long photoperiod. Daily profiles in the content of the main 5-HT oxidative metabolite, the 5-hydroxyindoleacetic acid (5-HIAA), outlined those of the amine precursor. The chronograms of both aminergic compounds contrast with those of 5-hydroxytryptophan content, which displayed a net tendency to increase at night. This study also provides evidence for the existence of daily cyclic changes in the content of 5-methoxytryptamine (5-MT), 5-methoxyindoleacetic acid (5-MIAA), and 5-methoxytryptophol (5-MTOL) in trout pineal organ, which were also dependent on photoperiod. The 24-h profiles in 5-MT content correlated well with those of 5-HT, showing a peak at the first hour of darkness in all photoperiodic conditions, and a decay at midnight only in both neutral and long photoperiods. Similarly, the content of 5-MTOL also displayed high values during the day-night transition in trout kept under neutral and long photoperiods, followed by a slow decay all along the night. Finally, levels of 5-MIAA increased in all photoperiods when lights were turned off, being this nocturnal increase maximal in fish kept under LD 16:08. These results suggest that light-dark cycle modulates daily rhythms in pineal indoles and non-melatonin 5-methoxyindoles by acting mainly through the melatonin synthesis activity, which limits the availability of 5-HT for the oxidative and direct methylation pathways. In addition, it seems that a nocturnally increased synthesis of 5-HT might be a requirement for the optimal formation of melatonin and other 5-methoxyindoles in the pineal organ when trout remain under short photoperiods.
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Affiliation(s)
- Rosa M Ceinos
- Laboratorio de Fisiología Animal, Departamento Biología Funcional y CC Salud, Facultad de Biología, Universidad de Vigo, 36200 Vigo, Spain
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Lutterschmidt DI, LeMaster MP, Mason RT. Effects of melatonin on the behavioral and hormonal responses of red-sided garter snakes (Thamnophis sirtalis parietalis) to exogenous corticosterone. Horm Behav 2004; 46:692-702. [PMID: 15555513 DOI: 10.1016/j.yhbeh.2004.06.013] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2004] [Revised: 06/14/2004] [Accepted: 06/16/2004] [Indexed: 12/12/2022]
Abstract
We investigated possible interactions between melatonin and corticosterone in modulating the reproductive behavior of male red-sided garter snakes (Thamnophis sirtalis parietalis) following spring emergence. We also examined whether melatonin's modulatory actions could be explained by its potential properties as a serotonin receptor antagonist. Exogenous corticosterone significantly reduced courtship behavior of male snakes in a dose-dependent manner. Melatonin also significantly reduced courtship behavior of male garter snakes. Pretreatment with melatonin before administering corticosterone treatments further suppressed courtship behavior of red-sided garter snakes. These results indicate additive inhibitory effects of melatonin and corticosterone in modulating reproductive behavior. Snakes receiving ketanserin, a serotonergic type 2A receptor antagonist, followed by corticosterone also showed reduced courtship behavior; this serotonin receptor antagonist followed by treatment with vehicle did not significantly influence courtship behavior of male snakes. Neither melatonin nor corticosterone treatments significantly influenced testosterone + 5-alpha-dihydrotestosterone concentrations of male garter snakes, supporting a direct effect of melatonin and corticosterone on courtship behavior that is independent of any effect on androgen concentrations. We propose that a serotonin system is involved in the modulation of male courtship behavior by melatonin and corticosterone. In addition, our data support the hypothesis that melatonin may function as a serotonin receptor antagonist. Further research is necessary to discern whether the actions of melatonin and corticosterone are converging on the same pathway or if their effects on different pathways are having additive inhibitory effects on courtship behavior.
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15
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Saito D, Shi Q, Ando H, Urano A. Attenuation of diurnal rhythms in plasma levels of melatonin and cortisol, and hypothalamic contents of vasotocin and isotocin mRNAs in pre-spawning chum salmon. Gen Comp Endocrinol 2004; 137:62-8. [PMID: 15094336 DOI: 10.1016/j.ygcen.2004.02.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/06/2004] [Revised: 02/09/2004] [Accepted: 02/23/2004] [Indexed: 10/26/2022]
Abstract
In the present study, diurnal changes in plasma levels of melatonin and cortisol, and hypothalamic contents of neurohypophysial hormone mRNAs were examined in pre-spawning chum salmon, Oncorhynchus keta. From late November to early December, homing fish were captured at two sites along their migratory pathway on the Sanriku coast, Japan. Fish captured in the seawater (SW) environment were transferred to SW aquaria, and fish captured in the freshwater (FW) environment were to FW aquaria. They were maintained under natural photoperiod of approximately 10L:14D and sacrificed at 4-h interval through 24-h period. Plasma levels of melatonin were determined by radioimmunoassay, while cortisol levels were determined by enzyme immunoassay. Hypothalamic contents of vasotocin and isotocin mRNAs were determined by quantitative dot-blot hybridization assay. The melatonin levels showed weak nocturnal elevations in the SW and FW males, and FW females. The levels were maximal at 22:00 and minimal at 10:00 or 14:00, however the amplitudes were smaller than those reported in the previous studies using immature salmonids. The levels of vasotocin and isotocin mRNAs were higher in the males at all time points. The mRNA levels, however, did not show any diurnal variations in either of group. The same applied to plasma cortisol levels. These results indicate that the diurnal endocrine rhythms were attenuated in pre-spawning chum salmon, in contrast to the prominent diurnal rhythms in immature salmonids.
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Affiliation(s)
- Daisuke Saito
- Division of Biological Sciences, Hokkaido University Graduate School of Science, Sapporo, Hokkaido 060-0810, Japan.
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16
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Bertolucci C, Wagner G, Foà A, Gwinner E, Brandstätter R. Photoperiod affects amplitude but not duration of in vitro melatonin production in the ruin lizard (Podarcis sicula). J Biol Rhythms 2003; 18:63-70. [PMID: 12568245 DOI: 10.1177/0748730402239677] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The pineal gland and its major output signal melatonin have been demonstrated to play a central role in the seasonal organization of the ruin lizard Podarcis sicula. Seasonal variations in the amplitude of the nocturnal melatonin signal, with high values in spring as compared to low values in summer and autumn, have been found in vivo. The authors examined whether the pineal gland of the ruin lizard contains autonomous circadian oscillators controlling melatonin synthesis and whether previously described seasonal variations of in vivo melatonin production can also be found in isolated cultured pineal glands obtained from ruin lizards in summer and winter. In vitro melatonin release from isolated pineal glands of the ruin lizard persisted for 4 days in constant conditions. Cultured explanted pineal glands obtained from animals in winter and summer showed similar circadian rhythms of melatonin release, characterized by damping of the amplitude of the melatonin rhythm. Although different photoperiodic conditions were imposed on ruin lizards before explantation of pineal glands, the authors did not find any indication for corresponding differences in the duration of elevated melatonin in vitro. Differences were found in the amplitude of in vitro melatonin production in light/dark conditions and, to a lesser degree, in constant conditions. The presence of a circadian melatonin rhythm in vitro in winter, although such a rhythm is absent in vivo in winter, suggests that pineal melatonin production is influenced by an extrapineal oscillator in the intact animal that may either positively or negatively modulate melatonin production in summer and winter, respectively.
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Affiliation(s)
- C Bertolucci
- Department of Biology and Neuroscience Centre, University of Ferrara, Italy
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17
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Lutterschmidt DI, Lutterschmidt WI, Hutchison VH. Melatonin and thermoregulation in ectothermic vertebrates: a review. CAN J ZOOL 2003. [DOI: 10.1139/z02-189] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Precise behavioral thermoregulation is well documented in many ectothermic vertebrates. However, many complexities involving the influence of the pineal gland and melatonin (MEL) on thermoregulatory behavior, and thus body temperature (Tb), remain unresolved. Although MEL is commonly considered to decrease Tb in both endotherms and ectotherms, several ectothermic species do not modulate Tb in response to MEL. Furthermore, it is not yet clear how MEL integrates thermoregulatory behavior with environmental stimuli or how it modulates Tb. Some inferences about MEL action in endotherms are not applicable to ectotherms. Changes in ectothermic Tb are mediated primarily through behavioral modulation (not physiological modulation as in endotherms). Thus, the most likely mechanism underlying MEL's actions on ectothermic Tb is adjustment of the temperature set point in the hypothalamus. We provide a review of the literature addressing the effects of MEL on thermoregulatory behavior in ectothermic vertebrates. We also discuss mechanisms underlying MEL's influence on physiological and behavioral processes in ectotherms and hypotheses regarding interspecific differences in pineal complex and MEL function.
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18
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Rensing L, Ruoff P. Temperature effect on entrainment, phase shifting, and amplitude of circadian clocks and its molecular bases. Chronobiol Int 2002; 19:807-64. [PMID: 12405549 DOI: 10.1081/cbi-120014569] [Citation(s) in RCA: 195] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Effects of temperature and temperature changes on circadian clocks in cyanobacteria, unicellular algae, and plants, as well as fungi, arthropods, and vertebrates are reviewed. Periodic temperature with periods around 24 h even in the low range of 1-2 degrees C (strong Zeitgeber effect) can entrain all ectothermic (poikilothermic) organisms. This is also reflected by the phase shifts-recorded by phase response curves (PRCs)-that are elicited by step- or pulsewise changes in the temperature. The amount of phase shift (weak or strong type of PRC) depends on the amplitude of the temperature change and on its duration when applied as a pulse. Form and position of the PRC to temperature pulses are similar to those of the PRC to light pulses. A combined high/low temperature and light/dark cycle leads to a stabile phase and maximal amplitude of the circadian rhythm-when applied in phase (i.e., warm/light and cold/dark). When the two Zeitgeber cycles are phase-shifted against each other the phase of the circadian rhythm is determined by either Zeitgeber or by both, depending on the relative strength (amplitude) of both Zeitgeber signals and the sensitivity of the species/individual toward them. A phase jump of the circadian rhythm has been observed in several organisms at a certain phase relationship of the two Zeitgeber cycles. Ectothermic organisms show inter- and intraspecies plus seasonal variations in the temperature limits for the expression of the clock, either of the basic molecular mechanism, and/or the dependent variables. A step-down from higher temperatures or a step-up from lower temperatures to moderate temperatures often results in initiation of oscillations from phase positions that are about 180 degrees different. This may be explained by holding the clock at different phase positions (maximum or minimum of a clock component) or by significantly different levels of clock components at the higher or lower temperatures. Different permissive temperatures result in different circadian amplitudes, that usually show a species-specific optimum. In endothermic (homeothermic) organisms periodic temperature changes of about 24 h often cause entrainment, although with considerable individual differences, only if they are of rather high amplitudes (weak Zeitgeber effects). The same applies to the phase-shifting effects of temperature pulses. Isolated bird pineals and rat suprachiasmatic nuclei tissues on the other hand, respond to medium high temperature pulses and reveal PRCs similar to that of light signals. Therefore, one may speculate that the self-selected circadian rhythm of body temperature in reptiles or the endogenously controlled body temperature in homeotherms (some of which show temperature differences of more than 2 degrees C) may, in itself, serve as an internal entraining system. The so-called heterothermic mammals (undergoing low body temperature states in a daily or seasonal pattern) may be more sensitive to temperature changes. Effects of temperature elevation on the molecular clock mechanisms have been shown in Neurospora (induction of the frequency (FRQ) protein) and in Drosophila (degradation of the period (PER) and timeless (TIM) protein) and can explain observed phase shifts of rhythms in conidiation and locomotor activity, respectively. Temperature changes probably act directly on all processes of the clock mechanism some being more sensitive than the others. Temperature changes affect membrane properties, ion homeostasis, calcium influx, and other signal cascades (cAMP, cGMP, and the protein kinases A and C) (indirect effects) and may thus influence, in particular, protein phosphorylation processes of the clock mechanism. The temperature effects resemble to some degree those induced by light or by light-transducing neurons and their transmitters. In ectothermic vertebrates temperature changes significantly affect the melatonin rhythm, which in turn exerts entraining (phase shifting) functions.
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Affiliation(s)
- Ludger Rensing
- Institute of Cell Biology, Biochemistry and Biotechnology, University of Bremen, Germany.
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Abstract
The study of reproductive diseases of chelonians has become increasingly sophisticated in the last decade. Widespread captive breeding has increased the number of reproductive problems presented to veterinarians. Advances in the level of veterinary care have encouraged chelonians owners to seek solutions to problems that may have previously been considered unsolvable. Improved diagnostic imaging, particularly radiography, ultrasonography and endoscopy, have made visualization and diagnosis of reproductive disease easier. Better quality veterinary care has made treatment of chelonian diseases more sophisticated which has lead to improved methods of anesthesia, surgery, and medicine. Concerns over rapidly diminishing chelonian populations and habitat have made the need for study of reproduction a higher priority; veterinary medicine has gained from this research.
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Affiliation(s)
- Charles J Innis
- VCA Westboro Animal Hospital, Tufts University School of Veterinary Medicine, Westboro, North Grafton, MA, USA
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20
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Hau M, Romero LM, Brawn JD, Van't Hof TJ. Effect of polar day on plasma profiles of melatonin, testosterone, and estradiol in high-Arctic Lapland Longspurs. Gen Comp Endocrinol 2002; 126:101-12. [PMID: 11944971 DOI: 10.1006/gcen.2002.7776] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In polar habitats, continuous daylight (polar day) can prevail for many weeks or months around the summer solstice. In the laboratory, continuous light conditions impair or disrupt circadian rhythms in many animals. To determine whether circadian rhythms are disrupted under natural polar day conditions in a species that is only a summer resident in polar regions we analyzed diel rhythms in plasma concentrations of melatonin, testosterone (T), and 17-beta estradiol (E(2)) during the summer solstice in Arctic-breeding Lapland Longspurs (Calcarius lapponicus). We compared these profiles to those of conspecifics housed in outdoor aviaries at a mid-latitude site in Seattle, Washington, during spring, summer, fall, and winter. Under polar day conditions plasma melatonin concentrations of Lapland Longspurs were strongly suppressed, but still showed a significant diel rhythm. Likewise, plasma T in males, and E(2) in females, showed significant diel changes in Arctic birds. Lapland Longspurs housed at mid-latitude in Seattle showed high-amplitude melatonin cycles at all times of the year, and the duration of the nightly melatonin secretion was positively correlated with the duration of the dark phase. We found no diel changes in plasma T in Seattle males in May, but Seattle females showed significant day/night differences in plasma E(2) in May. The data suggest that even under polar day conditions diel rhythms can persist. The maintenance of hormone rhythms could provide a physiological basis to reports of rhythmic behavior in many birds during the Arctic summer.
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Affiliation(s)
- Michaela Hau
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey 08544, USA.
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21
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Lutterschmidt DI, Lutterschmidt WI, Ford NB, Hutchison VH. Behavioral thermoregulation and the role of melatonin in a nocturnal snake. Horm Behav 2002; 41:41-50. [PMID: 11863382 DOI: 10.1006/hbeh.2001.1721] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Daily and seasonal variations in hormone levels influence the complex interactions between behavior and physiology. Ectothermic animals possess the unique ability behaviorally to adjust body temperature (T(b)) to control physiological rate processes. Thus, a hormone may indirectly influence a physiological rate by directly influencing the behaviors that adjust or control that rate process. Although many hormonal influences on behavioral regulation of T(b) remain uninvestigated, melatonin (MEL) generally is considered a hormone that decreases mean preferred T(b). Many ectotherms demonstrate the selection of lower T(b)'s in response to increased MEL concentrations. Here, we examined the influence of MEL on the behavioral regulation of T(b) in the nocturnal African house snake Lamprophis fuliginosus. A series of experiments with two injection regimes of MEL had no significant effect on the mean preferred T(b) of L. fuliginosus. In addition, mean preferred T(b)'s during the photophase did not differ significantly from those during scotophase. Our findings suggest that L. fuliginosus does not respond to elevated concentrations of either endogenous or exogenous MEL. To verify that the African house snake is nocturnal, we investigated activity patterns of L. fuliginosus throughout the photoperiod. The activity period of L. fuliginosus occurs in the scotophase of the photoperiod, a pattern consistent with that of nocturnal species. This suggests that nocturnal organisms such as L. fuliginosus may not respond to MEL in the same manner as many diurnal species. Our results support the hypothesis that some animals, particularly nocturnal species, may have developed alternative responses to increased plasma concentrations of MEL.
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Firth BT, Belan I, Kennaway DJ, Moyer RW. Thermocyclic entrainment of lizard blood plasma melatonin rhythms in constant and cyclic photic environments. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 277:R1620-6. [PMID: 10600907 DOI: 10.1152/ajpregu.1999.277.6.r1620] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We assessed how chronic exposure to 6-h cryophase temperatures of 15 degrees C in an otherwise 33 degrees C environment entrains the rhythm of blood plasma melatonin rhythms in lizards (Tiliqua rugosa) subjected to constant dark (DD), constant light (LL), and to 12:12-h light-dark cycles (12L:12D). The peak of the melatonin rhythm was entrained by the cryophase temperature of the thermocycle in DD and LL, irrespective of the time at which the cryophase temperature was applied. Comparable thermocycles of 6 h at 15 degrees C imposed on a 12L:12D photocycle, however, affected the amplitude and phase of the melatonin rhythm, depending on the phase relationship between light and temperature. Cold pulses in the early light period and at midday resulted, respectively, either in low amplitude or nonexistent melatonin rhythms, whereas those centered in or around the dark phase elicited rhythms of high amplitude. Supplementary experiments in 12L:12D using two intermittent 6-h 15 degrees C cryophases, one delivered in the midscotophase and another in the midphotophase, elicited melatonin rhythms comparable to those in lizards subjected to constant 33 degrees C and 12L:12D. In contrast, lizards subjected to 12L:12D and a 33 degrees C:15 degrees C thermocycle, whose thermophase was aligned with the photophase, produced a threefold increase in the amplitude of the melatonin rhythm. Taken together, these results support the notion that there is an interaction between the external light and temperature cycle and a circadian clock in determining melatonin rhythms in Tiliqua rugosa.
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Affiliation(s)
- B T Firth
- Department of Anatomical Sciences, University of Adelaide, Adelaide, SA 5005, Australia.
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23
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Abstract
Daily rhythms are a fundamental feature of all living organisms; most are synchronized by the 24 hr light/dark (LD) cycle. In most species, these rhythms are generated by a circadian system, and free run under constant conditions with a period close to 24 hr. To function properly the system needs a pacemaker or clock, an entrainment pathway to the clock, and one or more output signals. In vertebrates, the pineal hormone melatonin is one of these signals which functions as an internal time-keeping molecule. Its production is high at night and low during day. Evidence indicates that each melatonin producing cell of the pineal constitutes a circadian system per se in non-mammalian vertebrates. In addition to the melatonin generating system, they contain the clock as well as the photoreceptive unit. This is despite the fact that these cells have been profoundly modified from fish to birds. Modifications include a regression of the photoreceptive capacities, and of the ability to transmit a nervous message to the brain. The ultimate stage of this evolutionary process leads to the definitive loss of both the direct photosensitivity and the clock, as observed in the pineal of mammals. This review focuses on the functional properties of the cellular circadian clocks of non-mammalian vertebrates. How functions the clock? How is the photoreceptive unit linked to it and how is the clock linked to its output signal? These questions are addressed in light of past and recent data obtained in vertebrates, as well as invertebrates and unicellulars.
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Affiliation(s)
- J Falcón
- CNRS UMR 6558, Département des Neurosciences, Université de Poitiers, France.
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24
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Lutterschmidt WI, Lutterschmidt DI, Tracy CR, Hutchison VH. Time course analyses of the thermoregulatory responses to melatonin and chlorpromazine in bull snakes (Pituophis melanoleucus). J Therm Biol 1998. [DOI: 10.1016/s0306-4565(98)00017-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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25
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Mayer I, Bornestaf C, Borg B. Melatonin in non-mammalian vertebrates: Physiological role in reproduction? ACTA ACUST UNITED AC 1997. [DOI: 10.1016/s0300-9629(96)00468-9] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Vivien-Roels B, Pitrosky B, Zitouni M, Malan A, Canguilhem B, Bonn D, Pévet P. Environmental control of the seasonal variations in the daily pattern of melatonin synthesis in the European hamster, Cricetus cricetus. Gen Comp Endocrinol 1997; 106:85-94. [PMID: 9126468 DOI: 10.1006/gcen.1996.6853] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Nocturnal patterns of pineal melatonin concentrations were measured at hourly intervals in the European hamster, Cricetus cricetus, maintained under different natural or experimental environmental conditions. There were pronounced variations in the night peak of pineal melatonin both in the duration and the amplitude of the melatonin peak and in the onset and decline of melatonin synthesis. The duration of the melatonin peak increased proportionally with increased dark period. The amplitude increased abruptly from LD 16/8 to LD 15/9 and remained constant in all other photoperiods. The onset of synthesis started 6:00 hours after the onset of darkness in LD 16/8, 15/9, and 14/10, while it started 4:00 hours after dark onset in shorter photoperiods (LD 12/12 and 10/14). This result is opposite to that observed in the rat. The decline of synthesis was delayed as darkness increased and was directly related to lights on in long photoperiods, while it was endogenous in short photoperiods. Temperature, under a long photoperiod, also seems to be implicated in the regulation of the amplitude of the melatonin peak.
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Affiliation(s)
- B Vivien-Roels
- URA-CNRS 1332, Neurobiologie des fonctions rythmiques et saisonnières, Université Louis Pasteur, Strasbourg, France.
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28
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Falcón J, Bolliet V, Collin JP. Partial characterization of serotonin N - acetyltransferases from northern pike (Esox lucius, L.) pineal organ and retina: effects of temperature. Pflugers Arch 1996; 432:386-93. [PMID: 8765997 DOI: 10.1007/s004240050149] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
In vertebrates, the nocturnal rise in pineal organ and retinal melatonin synthesis results from the increase in the activity of the serotonin N-acetyltransferase (NAT), a cAMP-dependent enzyme. In the fish pineal organ in culture, light and temperature act in a similar manner on cAMP content and NAT activity. It is not known whether the effects of temperature are mediated through cAMP or through modifications of NAT kinetics. The present study was designed: (1) to find out whether NAT activity from pineal organ homogenates is similar to NAT activity from pineal organs in culture, with regard to variations in temperature, and (2) to compare NAT activity from the pineal organ and the retina. Pineal organ and retinal NAT activity increased linearly with protein concentrations. Higher activities were obtained with 0.2 mol/l of phosphate buffer, pH 6. Higher molarity or a higher pH induced a decrease in retinal and pineal organ NAT activity: retinal NAT was more sensitive than pineal organ NAT to changes in molarity, whereas the opposite held true as far as pH was concerned. Pineal organ and retinal NAT obeyed the Michaelis-Menten equation with respect to increasing concentrations of acetyl-coenzyme A. With increasing concentrations of tryptamine: (1) pineal organ NAT activity increased in a manner suggesting positive co-operativity, (2) retinal NAT displayed, after an initial increase, inhibition by substrate. The kinetics of the reactions were temperature dependent. Maximal activities were reached at 18/20 degrees C in the pineal organ and at 37 degrees C in the retina. The present study is the first to describe the optimum conditions for the assay of NAT activity in homogenates from the retina of fish and from the pineal organ of poikilotherms, and also the first to compare some characteristics of NAT activity from these two analogous organs. Our results suggest that the effects of temperature on melatonin production are mediated, at least in part, through modifications of NAT kinetics. Future studies will aim to clarify whether the activities measured in the pineal organ and retinal homogenates reflect the presence of one or of several enzymes.
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Affiliation(s)
- J Falcón
- Laboratoire de Neurobiologie et Neuroendocrinologie Cellulaires, URA CNRS 1869,
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29
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Abstract
The pineal gland of poikilothermic vertebrates originates as an evagination from the diencephalic roof between the habenular and the posterior commissures, and associates with a parapineal organ to form the so-called pineal complex. The pinealocytes may be photosensitive, secretory or intermediate cells between both. Melatonin, the indoleamine secreted by the pineal, exhibits a circadian secretory rhythm that conveys environmental information to the organism. The peak melatonin secretion occurs during the night, although there are a few examples of an increase in indoleamine secretion during the day. Melatonin is also synthesized in other sites such as the retina, and it has been found in many invertebrates and unicellular organisms. The rhythmic secretory pattern of melatonin is responsible for many biological rhythms exhibited by lower vertebrates. These rhythms are abolished by pinealectomy in some species, but not in others, suggesting the existence of an extra-pineal pacemaker. The photoperiod and the temperature (especially in reptiles) are the main environmental factors affecting the secretory rhythm of melatonin. Poikilothermic vertebrates exhibit a circadian rhythmic color change, with nocturnal blanching, usually related to melatonin secretion. In amphibians, melatonin exhibits a potent skin lightening activity. However, in fishes and reptiles the melatonin effects vary with the species, the developmental stage, and the pigment cell location. Melatonin also exerts inhibitory or excitatory activity on the amphibian reproductive system, regulation of circadian locomotory activity in reptiles, and modulation of the amphibian metamorphosis. Melatonin has also a modulatory effect on the response of target cells to different hormones and high concentrations or prolonged exposure to the indoleamine may cause autodesensitization in various tissues. Binding sites of melatonin have been detected in the central nervous system and peripheral tissues of various vertebrates. The relative potencies of melatonin analogues demonstrated two subtypes of melatonin receptors (ML-1 and ML-2). A transmembrane melatonin receptor has been cloned from Xenopus laevis melanophores; it belongs to the family of the G protein-coupled receptors and exhibits 85% homology with the mammalian nervous system receptor. Melatonin binding sites in the nucleus of many cell types and its potent intracellular anti-oxidant action suggest mechanisms of action other than through the G-protein coupled receptor.
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Affiliation(s)
- A M Filadelfi
- Dep. Fisiologia, Inst. Biociências, Universidade de Săo Paulo, Brasil
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30
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Bolliet V, Ali MA, Lapointe FJ, Falcón J. Rhythmic melatonin secretion in different teleost species: an in vitro study. J Comp Physiol B 1996; 165:677-83. [PMID: 8882513 DOI: 10.1007/bf00301136] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The rhythmic production of melatonin is governed by intrapineal oscillators in all fish species so far investigated except the rainbow trout. To determine whether the latter represents an exception among fish, we measured in vitro melatonin secretion in pineal organs of nine wild freshwater and six marine teleost species cultured at constant temperature and under different photic conditions. The results demonstrate that pineal organs of all species maintain a rhythmic secretion of melatonin under light:dark cycles and complete darkness, and strongly suggest that most fish possess endogenous intrapineal oscillators driving the rhythm of melatonin production, with the exception of the rainbow trout.
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Affiliation(s)
- V Bolliet
- Département de Sciences Biologiques, Université de Montréal, Canada
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31
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Larson-Prior LJ, Siuciak JA, Dubocovich ML. Localization of 2-[125I]iodomelatonin binding sites in visual areas of the turtle brain. Eur J Pharmacol 1996; 297:181-5. [PMID: 8851181 DOI: 10.1016/0014-2999(95)00820-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The hormone melatonin is believed to play an important role in the regulation of both circadian and circannual rhythms. In mammalian vertebrates melatonin receptors are discretely localized, with broader distributions reported in avians and reptiles. To examine the sites at which melatonin may act in the turtle brain, 2-[125I]iodomelatonin binding sites were assessed using quantitative autoradiography. Specific binding sites were primarily restricted to forebrain structures with a wide distribution in visual recipient areas. The distribution of melatonin sensitive sites within the turtle visual system suggests that the ability to transduce received photoperiodic signals in the reptilian brain is broadly distributed within the central nervous system.
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Affiliation(s)
- L J Larson-Prior
- Department of Neuroscience and Anatomy, Pennsylvania State University, Hershey 17033, USA
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32
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Mendonça MT, Tousignant AJ, Crews D. Pinealectomy, melatonin, and courtship behavior in male red-sided garter snakes (Thamnophis sirtalis parietalis). THE JOURNAL OF EXPERIMENTAL ZOOLOGY 1996; 274:63-74. [PMID: 8583209 DOI: 10.1002/(sici)1097-010x(19960101)274:1<63::aid-jez7>3.0.co;2-d] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Activation of courtship behavior in male red-sided garter snakes is independent of androgens. Only exposure to extended periods of low temperature with subsequent warming stimulates courtship in males. The pineal gland is thought to transduce temperature as well as photoperiodic information in reptiles. Therefore, we explored the relationship of the pineal and melatonin to sexual behavior in this species. Pinealectomy of male garter snakes disrupted sexual behavior upon emergence from a 17-week period of low temperature in approximately 60% of treated individuals in each of the 3 years of study. However, 40% of the males were unaffected by the pinealectomy, engaging in vigorous courtship. Administration of exogenous, chronic melatonin did not significantly modulate the effect of pinealectomy. Upon pinealectomy in the autumn (before hibernation), plasma levels of melatonin fell. However, upon emergence from hibernation, melatonin levels in pinealectomized (PINX) and sham-treated (SHAM) animals were equivalent, indicating extrapineal source(s) of melatonin. However, PINX males did not exhibit a diel cycle in melatonin levels upon emergence. Instead, melatonin remained elevated through the subsequent 24-hr period. SHAMs did exhibit a diel cycle. Ten days after emergence, PINX animals either had a disrupted/abnormal melatonin cycle and were non-courters or had a cycle similar to SHAM males and courted. Therefore, a normal diel cycle of melatonin appeared necessary for the proper expression of courtship behavior. These results suggest that the pineal in snakes 1) is part of a complex, multi-oscillator system as it is in birds and lizards and 2) may play a role in maintaining polymorphism in timing of reproductive behavior.
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Affiliation(s)
- M T Mendonça
- Department of Zoology, University of Texas at Austin 78712, USA
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33
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Moyer RW, Firth BT, Kennaway DJ. Effect of constant temperatures, darkness and light on the secretion of melatonin by pineal explants and retinas in the gecko Christinus marmoratus. Brain Res 1995; 675:345-8. [PMID: 7796151 DOI: 10.1016/0006-8993(95)00073-y] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The effects of temperature and lighting conditions on the secretion of melatonin by the pineal organ of the nocturnal gecko Christinus marmoratus was studied using in vitro perifusion. In a 12L:12D lighting regime, a high-amplitude melatonin rhythm was detectable at a constant temperature of 20 and 30 degrees C but not at 10 or 37 degrees C. There were sustained high levels of melatonin in constant darkness and sustained low levels in constant light. No retinal melatonin was detected using static and perifusion culture techniques. These results show that the pineal organ of C. marmoratus maintains light sensitivity in vitro but does not contain an oscillator coupled to the melatonin synthetic pathway.
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Affiliation(s)
- R W Moyer
- Department of Anatomy and Histology, University of Adelaide, Australia
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34
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Iigo M, Aida K. Effects of season, temperature, and photoperiod on plasma melatonin rhythms in the goldfish, Carassius auratus. J Pineal Res 1995; 18:62-8. [PMID: 7629692 DOI: 10.1111/j.1600-079x.1995.tb00141.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Effects of season, environmental temperature, and photoperiod on plasma melatonin concentrations were studied in the goldfish, Carassius auratus. When goldfish were reared under natural conditions, melatonin levels at mid-dark exhibited seasonal changes, with higher levels obtained in June and September than in December and March. When fish were kept under light:dark (LD) cycle of 12:12 at 5, 15, or 25 degrees C during March-April, temperature-dependent increases in melatonin levels at mid-dark were observed. When animals were maintained under LD 16:8 or LD 8:16 in combination with temperature changes (5, 15, and 25 degrees C) during January-February, the duration of nocturnal elevation in melatonin was controlled by the length of the scotophase while the amplitude was influenced by environmental temperature. These results indicate that plasma melatonin profiles in the goldfish exhibit seasonal changes that are regulated by both photoperiod and temperature.
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Affiliation(s)
- M Iigo
- Department of Anatomy, St. Marianna University School of Medicine, Kawasaki, Japan
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35
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Filadelfi AM, Castrucci AM. Melatonin desensitizing effects on the in vitro responses to MCH, alpha-MSH, isoproterenol and melatonin in pigment cells of a fish (S. marmoratus), a toad (B. ictericus), a frog (R. pipiens), and a lizard (A. carolinensis), exposed to varying photoperiodic regimens. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. PART A, PHYSIOLOGY 1994; 109:1027-37. [PMID: 7828022 DOI: 10.1016/0300-9629(94)90252-6] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Melatonin is a weak dose-independent lightening agonist in fish skin, a moderate dose-dependent lightening agonist in toad skin and a potent lightening agent in frog and lizard skins (reversing in a dose-dependent manner the darkening caused by alpha-melanocyte-stimulating hormone). In frog skins, previous exposure to melatonin reduced further lightening actions of the indoleamine, and in toad skins, increasing concentrations of melatonin elicited decreasing lightening responses, suggesting an autodesensitizing action of the hormone. Various concentrations of melatonin diminished the responses to the lightening agonist melanin-concentrating hormone (MCH) in fish skins and to the darkening agonists alpha-MSH in toad, frog and lizard skins and isoproterenol in frog skins. In vitro inhibitory actions of melatonin are mimicked in the absence of the hormone in skin preparations from toads kept in continuous darkness for 48 hr. The lipophylic nature of the indoleamine associated with the results herein described suggests intracellular actions of melatonin on vertebrate pigment cells.
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Affiliation(s)
- A M Filadelfi
- Departamento de Fisiologia Geral, Universidade de São Paulo, Brazil
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36
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Valenciano AI, Alonso-Gómez AL, De Pedro N, Alonso-Bedate M, Delgado MJ. Serotonin N-acetyltransferase activity as a target for temperature in the regulation of melatonin production by frog retina. Pflugers Arch 1994; 429:153-9. [PMID: 7892099 DOI: 10.1007/bf00374306] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The adaptive mechanisms of serotonin N-acetyltransferase (NAT) activity in the regulation of melatonin synthesis in frog retina in the face of chronic and acute temperature changes have been investigated. We performed thermal acclimation experiments to test different environmental temperatures at two seasons of the year (summer and winter), followed by the set-up of an eyecup culture system to investigate the acute effects of temperature on NAT activity and melatonin production daily rhythms. Low temperature induced a significant increase in NAT activity, independent of both the time of the photocycle (midday or midnight) and the season of the year (winter or summer). Acute cold-induced stimulation of NAT activity may be associated with lower decreases in the enzyme synthesis rate, rather than decreases in the degradation rate. In contrast, acclimation to warm temperature (25 degrees C) stimulated ocular melatonin production. Nocturnal melatonin production in eyecups cultured at 25 degrees C was significantly higher than in eyecups cultured at 5 degrees C. We suggest that this discrepancy in thermal regulation of melatonin synthesis can be justified by a seasonal variation in serotonin content within the photoreceptor cells, which determines the thermal response of melatonin production through changes in NAT kinetics.
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Affiliation(s)
- A I Valenciano
- Facultad de Biología, Universidad Complutense, Madrid, Spain
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37
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Bidmon HJ, Stumpf WE. Distribution of target cells for 1,25-dihydroxyvitamin D3 in the brain of the yellow bellied turtle Trachemys scripta. Brain Res 1994; 640:277-85. [PMID: 8004456 DOI: 10.1016/0006-8993(94)91883-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Five h after injection of tritiated 1,25-dihydroxyvitamin D3 into Trachemys scripta, neurons with nuclear concentrations of radioactivity were identified in distinct regions within the central nervous system. Coinjection of a 100-fold excess of non-labeled 1,25-dihydroxyvitamin D3 abolished or reduced the specific nuclear binding of tracer. Target neurons were present in ventral periventricular brain regions including tuberculum olfactorium, nucleus accumbens, cortex piriformis, primordium hippocampi, nucleus striae terminalis, dorsal ventricular ridge, amygdala, nucleus infundibularis and tectum opticum. With the exception of the nucleus infundibularis and the tectum opticum, target neurons can be continuously followed from the ventrolateral nucleus accumbens throughout the nucleus striae terminalis into the amygdala. The general distribution of target neurons is similar to that described for rodents but more restricted to the above regions. The results show that target neurons for vitamin D are located in brain regions including several components of the limbic and thalamic systems in which gonadal steroids as well as aminergic and peptidergic messengers exert their actions. Vitamin D, the heliogenic steroid hormone, may therefore be involved in the orchestration of season-specific processes such as reproduction and related behaviors.
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Affiliation(s)
- H J Bidmon
- Institut für Neuroanatomie, Heinrich-Heine-Universität, Düsseldorf, FRG
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Hyde LL, Underwood H. Effects of nightbreak, T-cycle, and resonance lighting schedules on the pineal melatonin rhythm of the lizard Anolis carolinensis: correlations with the reproductive response. J Pineal Res 1993; 15:70-80. [PMID: 8283387 DOI: 10.1111/j.1600-079x.1993.tb00512.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Experiments were conducted to determine if a correlation exists between any aspect of the pineal melatonin rhythm (such as its duration or phase) in the lizard Anolis carolinensis and the reproductive response to photoperiod. The rhythm of pineal melatonin content was determined in anoles exposed to nightbreak lighting protocols (10L:5D:1L:8D, 10L:10D:1L:3D), resonance lighting cycles (LD 11:13, LD 11:25), and T-cycle lighting protocols (LD 11:7, LD 11:9, LD 11:13, LD 11:15, LD 11:19) and compared with the testicular response to these lighting protocols as determined previously [Underwood and Hyde, (1990) J. Comp. Physiol. (A) 167:231-243]. Different T-cycles and nightbreak cycles elicited changes in both the duration of the melatonin peak and the phase of the melatonin peak relative to these light cycles. The response to the resonance cycle (LD 11:25) was complex, probably due to the overlapping patterns of two groups whose pineal melatonin rhythms were entrained approximately 12 hr out of phase with each other. No correlation was observed between the duration, or the amplitude, of the nocturnal melatonin peaks seen on the various light cycles and the reproductive response to these cycles. A correlation was observed between the phase of the pineal melatonin rhythm and the reproductive response. Light cycles were inductive (stimulated testicular growth) when the entrained melatonin rhythm peaked near the light-to-dark or the dark-to-light transition, but they were not inductive when the melatonin rhythm peaked during the middle third of the night. These results suggest that if melatonin is involved in the transduction of photoperiodic information in Anolis, neither the duration nor amplitude of the nocturnal melatonin pulse is involved in the measurement of day length. Instead, the phase-relationship of the melatonin rhythm to the rest of the circadian system may determine photoperiodic responsiveness.
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Affiliation(s)
- L L Hyde
- Department of Zoology, North Carolina State University, Raleigh 27695-7617
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39
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Abstract
The paper briefly reviews the data which shows that the circadian production and secretion of melatonin by the pineal gland can impart both daily, i.e., clock, and seasonal, i.e., calendar, information to the organism. The paper summarizes the 3 patterns of nocturnal melatonin production that have been described. Clearly, regardless of the pattern of nocturnal melatonin production a particular species normally displays, the duration of nightime elevated melatonin is proportional to the duration of the night length. Since daylength under natural conditions changes daily the melatonin rhythm, which adjusts to the photoperiod sends time of year information to the organism. The melatonin receptors which subserve the clock message sent by the pineal gland in the form of a melatonin cycle may reside in the biological clock itself, namely, the suprachiasmatic nuclei (SCN). The melatonin receptors that mediate seasonal changes in reproductive physiology are presumably those that are located on the pars tuberalis cells of the anterior pituitary gland. Besides these receptors which likely mediate clock and calendar information, melatonin receptors have been described in other organs. Interestingly, the distribution of melatonin receptors is highly species-specific. Whereas the clock and calendar information that the melatonin cycle imparts to the organism relies on cell membrane receptors, a fact that is of some interest considering the high lipophilicity of melatonin, recent studies indicate that other functions of melatonin may require no receptor whatsoever.
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Affiliation(s)
- R J Reiter
- Department of Cellular and Structural Biology, University of Texas Health Science Center, San Antonio 78284-7762
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40
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Effect of temperature on ganglion cell activity in the photoreceptive pineal organ of rainbow trout oncorhynchus mykiss. ACTA ACUST UNITED AC 1993. [DOI: 10.1016/0300-9629(93)90417-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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41
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Thermal responses of achromatic ganglion cells in the photosensory pineal organ of rainbow trout oncorhynchus mykiss. ACTA ACUST UNITED AC 1993. [DOI: 10.1016/0300-9629(93)90418-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Teo EH, Carati C, Firth BT, Barbour RA, Gannon B. Vascularization of the pineal complex in the lizard Tiliqua rugosa. Anat Rec (Hoboken) 1993; 236:521-36. [PMID: 8363056 DOI: 10.1002/ar.1092360312] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The vascularization of the pineal complex in the lizard Tiliqua rugosa was investigated by vascular corrosion and latex casting techniques. The fine structure of the pineal capillaries was also studied by transmission electron microscopy. The pineal complex in T. rugosa consists of an elongated pineal gland proper and a separate, distinct parietal eye. The pineal complex derives an abundant blood supply from branches of the middle and posterior cerebral arteries. Scanning electron microscopy of vascular corrosion casts revealed a dense and extensive pineal capillary bed which drains ultimately into a wide longitudinal sinus suggesting an efficient pathway for the rapid removal of substances secreted by the gland. The parietal eye, which receives a unilateral left-sided blood supply from the unpaired anterior pineal artery, is shown to be a highly vascularized structure. The close morphological relationship between the pineal gland and dorsal sac, where the two structures apparently share the same blood vessels, suggests a functional relationship between them. The pineal capillaries are fenestrated with tight junctions between adjoining endothelial cells. Podia-like abluminal extensions of the endothelial cells were observed in close relation to unmyelinated nerve bundles. The basal margin of the pineal parenchyma is highly invaginated with thin finger-like cytoplasmic protrusions into the pericapillary space. Distinct bands of microfibrils form "struts" anchoring the pineal parenchyma to the endothelial wall. These features may have a role in the transfer of materials between the pineal gland and the blood stream.
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Affiliation(s)
- E H Teo
- Department of Anatomy and Histology, University of Adelaide, South Australia
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43
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Rawding RS, Hutchison VH. Influence of temperature and photoperiod on plasma melatonin in the mudpuppy, Necturus maculosus. Gen Comp Endocrinol 1992; 88:364-74. [PMID: 1490582 DOI: 10.1016/0016-6480(92)90231-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
A melatonin (MEL) radioimmunoassay employed previously only in mammals was used to estimate plasma MEL in a salamander, Necturus maculosus. Validation procedures included thin-layer chromatography of plasma extracts, parallel inhibition curves of authentic MEL and serially diluted plasma and plasma extracts and quantitative recovery of authentic MEL added to pooled Necturus plasma. A diel cycle of plasma MEL was demonstrated in mudpuppies acclimatized for a minimum of 3 weeks under a 12L:12D photoperiod and 15 +/- 1 degrees and sampled in late March. The MEL cycle persisted under a reversed photoperiod (lights on, 1800 hr), but the amplitude of the MEL peak was diminished, and the peak was more than 180 degrees out of phase with the corresponding peak under a normal photoperiod. In animals acclimated to 5 degrees in mid-June under a 12L:12D photoperiod, the diel cycle of plasma MEL continued, but both midphotophase and midscotophase concentrations were reduced compared with 15 degrees controls. The diel cycle was also present in animals acclimated to 25 degrees, but the decrease in MEL concentrations was less marked than that in 5 degrees animals. Photoperiod is apparently the primary cue for cycles in plasma MEL in Necturus, but the cycle can be influenced by temperature.
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Affiliation(s)
- R S Rawding
- Department of Zoology, University of Oklahoma, Norman 73019-0235
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Vivien-Roels B, Pevet P, Masson-Pevet M, Canguilhem B. Seasonal variations in the daily rhythm of pineal gland and/or circulating melatonin and 5-methoxytryptophol concentrations in the European hamster, Cricetus cricetus. Gen Comp Endocrinol 1992; 86:239-47. [PMID: 1601273 DOI: 10.1016/0016-6480(92)90107-u] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Day-night variations in pineal and/or circulating melatonin and 5-methoxytryptophol (5-ML) concentrations were measured monthly throughout the year in female European hamsters, Cricetus cricetus, maintained under natural conditions. Pronounced seasonal variations in the day-night rhythm of both melatonin and 5-ML were observed. As previously reported for melatonin, the daily rhythm of both methoxyindoles disappeared in spring and early summer, while a clear day-night rhythm occurred in autumn, winter, and early spring. The amplitude of the day-night variations appeared to be maximum from October until January. An inverse relationship existed between the rhythms of melatonin and 5-ML.
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Affiliation(s)
- B Vivien-Roels
- URA CNRS 1332, Université Louis Pasteur, Strasbourg, France
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Zachmann A, Falcon J, Knijff SC, Bolliet V, Ali MA. Effects of photoperiod and temperature on rhythmic melatonin secretion from the pineal organ of the white sucker (Catostomus commersoni) in vitro. Gen Comp Endocrinol 1992; 86:26-33. [PMID: 1505727 DOI: 10.1016/0016-6480(92)90122-z] [Citation(s) in RCA: 92] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The secretion rate of melatonin from cultured pineal organs of the white sucker was examined for several days under either a 12:12-hr light:dark (LD) cycle or continuous darkness (DD) at either 10 degrees or 20 degrees. The incubation medium was changed at 3-hr intervals and secreted melatonin was measured by RIA. Under a 12:12-hr LD cycle (0800 light on, 2000 light off) melatonin secretion was suppressed during the day and highly active at night, with larger amplitudes at 20 than at 10 degrees. In DD at 10 degrees no circadian rhythmicity in secretion was found in October or January, whereas at 20 degrees a circadian-like pattern was detected in pineals which were derived from animals reared at either 10 degrees or 20 degrees for 1 week prior to the experiment in October or January. The pineals in the DD experiment still responded to an additional 24-hr LD cycle at both temperatures even after 6 or more days. These results clearly reveal the influence of photoperiod and temperature on melatonin secretion of organ-cultured pineal glands. The existence of a circadian oscillator for melatonin secretion in the pineal gland of the white sucker is suggested.
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Affiliation(s)
- A Zachmann
- Département de Biologie, Université de Montréal, Québec, Canada
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46
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Miché F, Vivien-Roels B, Pévet P, Spehner C, Robin JP, Le Maho Y. Daily pattern of melatonin secretion in an antarctic bird, the emperor penguin, Aptenodytes forsteri: seasonal variations, effect of constant illumination and of administration of isoproterenol or propranolol. Gen Comp Endocrinol 1991; 84:249-63. [PMID: 1783270 DOI: 10.1016/0016-6480(91)90048-b] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Daily variations in circulating melatonin concentrations have been measured at monthly intervals from April to December 1986 in an Antarctic bird, the emperor penguin, Aptenodytes forsteri, maintained under natural conditions. Both duration of the elevated nighttime melatonin levels and amplitude of the day-night rhythm displays an annual variation closely related to variations in the daylength. Duration of the nocturnal peak of melatonin secretion depended upon the duration of the darkness, decreasing with increasing daylength and disappearing completely during the summer solstice. The duration of the nighttime melatonin peak melatonin increased inversely with decreasing daylength. The amplitude of the day-night rhythm decreased in such a way that the nocturnal peak of melatonin completely disappeared during the winter solstice. Three days of constant illumination in September did not suppress the nighttime peak of melatonin secretion. The response of melatonin secretion, decreasing after beta-adrenergic agonist treatment and increasing after antagonist treatment, reinforces the hypothesis that in birds the regulation of melatonin synthesis differs from that of the rat. Receptors other than beta receptors may be involved.
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Affiliation(s)
- F Miché
- URA-CNRS 1332, Université L. Pasteur, Strasbourg, France
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Firth BT, Kennaway DJ, Belan I. Thermoperiodic influences on plasma melatonin rhythms in the lizard Tiliqua rugosa: effect of thermophase duration. Neurosci Lett 1991; 121:139-42. [PMID: 2020370 DOI: 10.1016/0304-3940(91)90669-k] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Rhythms of plasma melatonin levels were determined in lizards (Tiliqua rugosa) subjected to a 12 h photocycle (12 h light: 12 h dark) at constant 33 degrees C, and at 7 different thermoperiods (33 degrees C thermophase and 15 degrees C cryophase) whose thermophase duration ranged from 1.5 to 21 h. The melatonin secretion rate, as measured by the amplitude and duration of elevated melatonin levels and the area under the curve, was maximal at thermoperiods whose thermophase was between 9 and 18 h in duration. The results indicate that in ectothermic vertebrates the prevailing thermoperiod as well as the photoperiod may influence melatonin rhythms and hence the timing of annual physiological cycles.
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Affiliation(s)
- B T Firth
- Department of Anatomy and Histology, University of Adelaide, Australia
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48
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The pineal and melatonin: regulators of circadian function in lower vertebrates. EXPERIENTIA 1990; 46:120-8. [PMID: 2404785 DOI: 10.1007/bf01955437] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The pineal has been identified as a major circadian pacemaker within the circadian system of a number of lower vertebrates although other pacemaking sites have been implicated as well. The rhythmic synthesis and secretion of the pineal hormone, melatonin, is suggested as the mechanism by which the pineal controls circadian oscillators located elsewhere. Both light and temperature cycles can entrain the pineal melatonin rhythm. The pineal, therefore, acts as a photo and thermoendocrine transducer which functions to synchronize internal cycle with cycles in the environment. A model is presented which portrays the pineal as a major component of a 'multioscillator' circadian system and which suggests how these multiple circadian clocks are coupled to each other and to cycles of light and temperature in the external world.
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49
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Firth BT, Kennaway DJ. Thermoperiod and photoperiod interact to affect the phase of the plasma melatonin rhythm in the lizard, Tiliqua rugosa. Neurosci Lett 1989; 106:125-30. [PMID: 2586818 DOI: 10.1016/0304-3940(89)90213-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Rhythms of plasma melatonin levels were determined in lizards (Tiliqua rugosa) subjected to 6 h thermocycles (6 h, 33 degrees C thermophase; 18 h, 15 degrees C cryophase) placed at 4 different phases of a 12 h photocycle (12 h light: 12 h dark). The peak of the melatonin rhythm was either shifted at different rates, or inhibited by the light phase of the photocycle, depending upon the phase relationship between the thermocycle and the photocycle. The results indicate that the pineal organ of ectotherms is part of a circadian pacemaker system, transducing photothermal environmental information into a neurochemical signal.
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Affiliation(s)
- B T Firth
- Department of Anatomy and Histology, University of Adelaide, S.A
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50
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The pineal and melatonin: Regulators of circadian function in lower vertebrates. ACTA ACUST UNITED AC 1989. [DOI: 10.1007/bf01953048] [Citation(s) in RCA: 85] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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