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Hibino S, Amiya N, Miyazaki Y, Nakano N, Yoneda M, Amano M, Yoshinaga T. Changes in Behavior and Diel Melatonin Secretion Toward Estivation in Western Sand Lance, Ammodytes japonicus (Uranoscopiformes, Ammodytidae). Zoolog Sci 2024; 41:245-250. [PMID: 38809862 DOI: 10.2108/zs230105] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2023] [Accepted: 02/07/2024] [Indexed: 05/31/2024]
Abstract
Western sand lance, Ammodytes japonicus, is known to have an estivation period, in which they cease feeding and stay in the sand from early summer to late autumn, followed by gonadal maturation. During the feeding period prior to estivation, they swim in daytime and spend the night in the sand. Before they start swimming, they show a typical behavior of head-exposing from the sand, which is likely to be related to foraging and predation avoidance. Our previous study revealed that melatonin regulates such diel behavior of this species. To elucidate the mechanisms of behavioral regulation throughout the life cycle of this sand lance, the present study examined the changes in behavior and melatonin secretion toward the estivation period. Both head-exposing and swimming behaviors were frequently observed at the transition period toward estivation. On the other hand, occurrence of these behaviors was suppressed just before entering estivation. Subsequently, it was found that plasma melatonin concentration was about three times higher at night than in daytime in the non-estivation period, while it was retained at high levels throughout the day in the estivation period. These results indicate that diurnal swimming behavior of sand lance from the feeding to estivation periods is associated with the daily cycle of melatonin secretion.
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Affiliation(s)
- Shizuha Hibino
- Graduate School of Marine Biosciences, Kitasato University, Kanagawa 252-0373, Japan
| | - Noriko Amiya
- Graduate School of Marine Biosciences, Kitasato University, Kanagawa 252-0373, Japan,
| | - Yoshiya Miyazaki
- Graduate School of Marine Biosciences, Kitasato University, Kanagawa 252-0373, Japan
| | - Nayu Nakano
- Graduate School of Marine Biosciences, Kitasato University, Kanagawa 252-0373, Japan
| | - Michio Yoneda
- Hakatajima Field Station, National Research Institute of Fisheries and Environment of Inland Sea, Japan Fisheries Research and Education Agency, Ehime 794-2305, Japan
| | - Masafumi Amano
- Graduate School of Marine Biosciences, Kitasato University, Kanagawa 252-0373, Japan
| | - Tatsuki Yoshinaga
- Graduate School of Marine Biosciences, Kitasato University, Kanagawa 252-0373, Japan
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Vazquez JI, Gascue V, Quintana L, Migliaro A. Understanding daily rhythms in weakly electric fish: the role of melatonin on the electric behavior of Brachyhypopomus gauderio. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2024; 210:7-18. [PMID: 37002418 DOI: 10.1007/s00359-023-01626-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Revised: 03/16/2023] [Accepted: 03/20/2023] [Indexed: 04/03/2023]
Abstract
Living organisms display molecular, physiological and behavioral rhythms synchronized with natural environmental cycles. Understanding the interaction between environment, physiology and behavior requires taking into account the complexity of natural habitats and the diversity of behavioral and physiological adaptations. Brachyhypopomus gauderio is characterized by the emission of electric organ discharges (EOD), with a very stable rate modulated by social and environmental cues. The nocturnal arousal in B. gauderio coincides with a melatonin-dependent EOD rate increase. Here, we first show a daily cycle in both the EOD basal rate (EOD-BR) and EOD-BR variability of B. gauderio in nature. We approached the understanding of the role of melatonin in this natural behavior through both behavioral pharmacology and in vitro assays. We report, for the first time in gymnotiformes, a direct effect of melatonin on the pacemaker nucleus (PN) in in vitro preparation. Melatonin treatment lowered EOD-BR in freely moving fish and PN basal rate, while increasing the variability of both. These results show that melatonin plays a key role in modulating the electric behavior of B. gauderio through its effect on rate and variability, both of which must be under a tight temporal regulation to prepare the animal for the challenging nocturnal environment.
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Affiliation(s)
- Juan I Vazquez
- Dpto de Neurofisiología Celular y Molecular, Instituto de Investigaciones Biológicas Clemente Estable, MEC, Montevideo, Uruguay
| | - Valentina Gascue
- Laboratorio de Neurociencias, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay
| | - Laura Quintana
- Dpto de Neurofisiología Celular y Molecular, Instituto de Investigaciones Biológicas Clemente Estable, MEC, Montevideo, Uruguay
| | - Adriana Migliaro
- Laboratorio de Neurociencias, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay.
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Amiya N, Matsuda E, Miyazaki Y, Nakano N, Kataoka M, Yamaji T, Amano M, Yoshinaga T. Circadian Rhythm and Endocrinological Control on the Swimming and Sand Burrowing Behaviors of Japanese Sand Lances Ammodytes spp. (Uranoscopiformes, Ammodytidae). Zoolog Sci 2023; 40:423-430. [PMID: 38064368 DOI: 10.2108/zs230053] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Accepted: 08/14/2023] [Indexed: 12/18/2023]
Abstract
In diurnal and nocturnal organisms, daily activity is regulated by the perception of environmental stimuli and circadian rhythms, which enable organisms to maintain their essential behaviors. The Japanese sand lances genus Ammodytes are coastal marine fish that exhibit unique nocturnal sand burrowing behavior. To elucidate the extrinsic and intrinsic regulation of this behavior and its endocrinological basis, we conducted a series of rearing experiments under various light conditions and hormone administrations. Under a light-dark photoperiod, the fish showed three types of behavior: sand buried, head-exposed from sand, and swimming/feeding. During the transition from dark to light periods, the fish first showed head exposure, followed by swimming and foraging, and buried themselves in the sand immediately after shifting to the dark period. Under constant light conditions, fish exhibited swimming behavior during the period corresponding to the acclimated light period. In addition, swimming did not occur under constant dark conditions but head exposure was observed at the time of the dark-light transition during acclimation. These observations indicate that the essential behavior of sand lances is regulated by both light and circadian rhythms. Subsequently, a melatonin-containing diet promoted the onset of burrowing in 10 to 120 min in a dose-dependent manner at 0.3-128 µg/g-diet, suggesting the direct behavioral regulation by this hormone. These findings suggest that the behavior of sand lances is strictly regulated by an intrinsic mechanism and that melatonin is a regulatory endocrine factor that induces burrowing behavior.
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Affiliation(s)
- Noriko Amiya
- School of Marine Biosciences, Kitasato University, Sagamihara, Kanagawa 252-0373, Japan,
| | - Eri Matsuda
- School of Marine Biosciences, Kitasato University, Sagamihara, Kanagawa 252-0373, Japan
| | - Yoshiya Miyazaki
- School of Marine Biosciences, Kitasato University, Sagamihara, Kanagawa 252-0373, Japan
| | - Nayu Nakano
- School of Marine Biosciences, Kitasato University, Sagamihara, Kanagawa 252-0373, Japan
| | - Masaki Kataoka
- School of Marine Biosciences, Kitasato University, Sagamihara, Kanagawa 252-0373, Japan
| | - Taichi Yamaji
- School of Marine Biosciences, Kitasato University, Sagamihara, Kanagawa 252-0373, Japan
| | - Masafumi Amano
- School of Marine Biosciences, Kitasato University, Sagamihara, Kanagawa 252-0373, Japan
| | - Tatsuki Yoshinaga
- School of Marine Biosciences, Kitasato University, Sagamihara, Kanagawa 252-0373, Japan
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Falcón J, Herrero MJ, Nisembaum LG, Isorna E, Peyric E, Beauchaud M, Attia J, Covès D, Fuentès M, Delgado MJ, Besseau L. Pituitary Hormones mRNA Abundance in the Mediterranean Sea Bass Dicentrarchus labrax: Seasonal Rhythms, Effects of Melatonin and Water Salinity. Front Physiol 2021; 12:774975. [PMID: 34975529 PMCID: PMC8715012 DOI: 10.3389/fphys.2021.774975] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Accepted: 11/12/2021] [Indexed: 11/13/2022] Open
Abstract
In fish, most hormonal productions of the pituitary gland display daily and/or seasonal rhythmic patterns under control by upstream regulators, including internal biological clocks. The pineal hormone melatonin, one main output of the clocks, acts at different levels of the neuroendocrine axis. Melatonin rhythmic production is synchronized mainly by photoperiod and temperature. Here we aimed at better understanding the role melatonin plays in regulating the pituitary hormonal productions in a species of scientific and economical interest, the euryhaline European sea bass Dicentrarchus labrax. We investigated the seasonal variations in mRNA abundance of pituitary hormones in two groups of fish raised one in sea water (SW fish), and one in brackish water (BW fish). The mRNA abundance of three melatonin receptors was also studied in the SW fish. Finally, we investigated the in vitro effects of melatonin or analogs on the mRNA abundance of pituitary hormones at two times of the year and after adaptation to different salinities. We found that (1) the reproductive hormones displayed similar mRNA seasonal profiles regardless of the fish origin, while (2) the other hormones exhibited different patterns in the SW vs. the BW fish. (3) The melatonin receptors mRNA abundance displayed seasonal variations in the SW fish. (4) Melatonin affected mRNA abundance of most of the pituitary hormones in vitro; (5) the responses to melatonin depended on its concentration, the month investigated and the salinity at which the fish were previously adapted. Our results suggest that the productions of the pituitary are a response to multiple factors from internal and external origin including melatonin. The variety of the responses described might reflect a high plasticity of the pituitary in a fish that faces multiple external conditions along its life characterized by marked daily and seasonal changes in photoperiod, temperature and salinity.
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Affiliation(s)
- Jack Falcón
- Biologie des Organismes et Ecosystèmes Aquatiques (BOREA), MNHN, CNRS UMR 8067, SU, IRD 207, UCN, UA, Paris, France
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins (BIOM), Banyuls-sur-Mer, France
| | - Maria Jesus Herrero
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins (BIOM), Banyuls-sur-Mer, France
| | - Laura Gabriela Nisembaum
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins (BIOM), Banyuls-sur-Mer, France
- Department of Genetics, Physiology and Microbiology, Complutense University of Madrid (UCM), Madrid, Spain
| | - Esther Isorna
- Department of Genetics, Physiology and Microbiology, Complutense University of Madrid (UCM), Madrid, Spain
| | - Elodie Peyric
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins (BIOM), Banyuls-sur-Mer, France
| | - Marilyn Beauchaud
- Equipe de Neuro-Ethologie Sensorielle, ENES/CRNL, CNRS UMR 5292, UMR-S 1028, Faculté des Sciences et Techniques, Université Jean-Monnet (UJM), Saint-Étienne, France
| | - Joël Attia
- Equipe de Neuro-Ethologie Sensorielle, ENES/CRNL, CNRS UMR 5292, UMR-S 1028, Faculté des Sciences et Techniques, Université Jean-Monnet (UJM), Saint-Étienne, France
| | - Denis Covès
- Station Ifremer de Palavas, Palavas-les-Flots, Nantes, France
| | - Michael Fuentès
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins (BIOM), Banyuls-sur-Mer, France
| | - Maria Jesus Delgado
- Department of Genetics, Physiology and Microbiology, Complutense University of Madrid (UCM), Madrid, Spain
| | - Laurence Besseau
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins (BIOM), Banyuls-sur-Mer, France
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Monroe AA, Schunter C, Welch MJ, Munday PL, Ravasi T. Molecular basis of parental contributions to the behavioural tolerance of elevated pCO 2 in a coral reef fish. Proc Biol Sci 2021; 288:20211931. [PMID: 34875194 PMCID: PMC8651409 DOI: 10.1098/rspb.2021.1931] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Accepted: 11/15/2021] [Indexed: 12/27/2022] Open
Abstract
Knowledge of adaptive potential is crucial to predicting the impacts of ocean acidification (OA) on marine organisms. In the spiny damselfish, Acanthochromis polyacanthus, individual variation in behavioural tolerance to elevated pCO2 has been observed and is associated with offspring gene expression patterns in the brain. However, the maternal and paternal contributions of this variation are unknown. To investigate parental influence of behavioural pCO2 tolerance, we crossed pCO2-tolerant fathers with pCO2-sensitive mothers and vice versa, reared their offspring at control and elevated pCO2 levels, and compared the juveniles' brain transcriptional programme. We identified a large influence of parental phenotype on expression patterns of offspring, irrespective of environmental conditions. Circadian rhythm genes, associated with a tolerant parental phenotype, were uniquely expressed in tolerant mother offspring, while tolerant fathers had a greater role in expression of genes associated with histone binding. Expression changes in genes associated with neural plasticity were identified in both offspring types: the maternal line had a greater effect on genes related to neuron growth while paternal influence impacted the expression of synaptic development genes. Our results confirm cellular mechanisms involved in responses to varying lengths of OA exposure, while highlighting the parental phenotype's influence on offspring molecular phenotype.
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Affiliation(s)
- Alison A. Monroe
- Division of Biological and Environmental Science and Engineering, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia
- Marine Genomics Laboratory, Department of Life Sciences, Texas A&M University Corpus Christi, Corpus Christi, TX 78412, USA
| | - Celia Schunter
- Swire Institute of Marine Science, The School of Biological Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong SAR
| | - Megan J. Welch
- Australian Research Council Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Australia
| | - Philip L. Munday
- Australian Research Council Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Australia
| | - Timothy Ravasi
- Australian Research Council Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Australia
- Marine Climate Change Unit, Okinawa Institute of Science and Technology Graduate University (OIST), 1919-1 Tancha, Onna-son, Okinawa 904-0495, Japan
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Saha S, Singh KM, Gupta BBP. Robust circadian and circannual rhythms of expression of clock genes and clock controlled aanat2 gene in the photoreceptive pineal organ of catfish, Clarias gariepinus under natural conditions. BIOL RHYTHM RES 2021. [DOI: 10.1080/09291016.2021.1911550] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Affiliation(s)
- Saurav Saha
- Environmental Endocrinology Laboratory, Department of Zoology, North-Eastern Hill University, Shillong, India
| | - Kshetrimayum Manisana Singh
- Environmental Endocrinology Laboratory, Department of Zoology, North-Eastern Hill University, Shillong, India
| | - Braj B. P. Gupta
- Environmental Endocrinology Laboratory, Department of Zoology, North-Eastern Hill University, Shillong, India
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Nisembaum LG, Martin P, Lecomte F, Falcón J. Melatonin and osmoregulation in fish: A focus on Atlantic salmon Salmo salar smoltification. J Neuroendocrinol 2021; 33:e12955. [PMID: 33769643 DOI: 10.1111/jne.12955] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Revised: 02/07/2021] [Accepted: 02/09/2021] [Indexed: 10/21/2022]
Abstract
Part of the life cycle of several fish species includes important salinity changes, as is the case for the sea bass (Dicentrarchus labrax) or the Atlantic salmon (Salmo salar). Salmo salar juveniles migrate downstream from their spawning sites to reach seawater, where they grow and become sexually mature. The process of preparation enabling juveniles to migrate downstream and physiologically adapt to seawater is called smoltification. Daily and seasonal variations of photoperiod and temperature play a role in defining the timing of smoltification, which may take weeks to months, depending on the river length and latitude. Smoltification is characterised by a series of biochemical, physiological and behavioural changes within the neuroendocrine axis. This review discusses the current knowledge and gaps related to the neuroendocrine mechanisms that mediate the effects of light and temperature on smoltification. Studies performed in S. salar and other salmonids, as well as in other species undergoing important salinity changes, are reviewed, and a particular emphasis is given to the pineal hormone melatonin and its possible role in osmoregulation. The daily and annual variations of plasma melatonin levels reflect corresponding changes in external photoperiod and temperature, which suggests that the hormonal time-keeper melatonin might contribute to controlling smoltification. Here, we review studies on (i) the impact of pinealectomy and/or melatonin administration on smoltification; (ii) melatonin interactions with hormones involved in osmoregulation (e.g., prolactin, growth hormone and cortisol); (iii) the presence of melatonin receptors in tissues involved in osmoregulation; and (iv) the impacts of salinity changes on melatonin receptors and circulating melatonin levels. Altogether, these studies show evidence indicating that melatonin interacts with the neuroendocrine pathways controlling smoltification, although more information is needed to clearly decipher its mechanisms of action.
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Affiliation(s)
- Laura Gabriela Nisembaum
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins, (BIOM), Banyuls-sur-Mer, France
| | - Patrick Martin
- Conservatoire National du Saumon Sauvage, Chanteuges, France
| | - Frédéric Lecomte
- Ministère des Forêts, de la Faune et des Parcs, Direction de l'expertise sur la faune aquatique, Québec, Canada
| | - Jack Falcón
- Biologie des Organismes et Ecosystèmes Aquatiques (BOREA), MNHN, CNRS 7208, SU, IRD 207, UCN, UA, Muséum National d'Histoire Naturelle, Paris, France
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Nisembaum LG, Martin P, Fuentes M, Besseau L, Magnanou E, McCormick SD, Falcón J. Effects of a temperature rise on melatonin and thyroid hormones during smoltification of Atlantic salmon, Salmo salar. J Comp Physiol B 2020; 190:731-748. [PMID: 32880666 DOI: 10.1007/s00360-020-01304-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 07/20/2020] [Accepted: 08/09/2020] [Indexed: 11/28/2022]
Abstract
Smoltification prepares juvenile Atlantic salmon (Salmo salar) for downstream migration. Dramatic changes characterize this crucial event in the salmon's life cycle, including increased gill Na+/K+-ATPase activity (NKA) and plasma hormone levels. The triggering of smoltification relies on photoperiod and is modulated by temperature. Both provide reliable information, to which fish have adapted for thousands of years, that allows deciphering daily and calendar time. Here we studied the impact of different photoperiod (natural, sustained winter solstice) and temperature (natural, ~ + 4° C) combinations, on gill NKA, plasma free triiodothyronine (T3) and thyroxine (T4), and melatonin (MEL; the time-keeping hormone), throughout smoltification. We also studied the impact of temperature history on pineal gland MEL production in vitro. The spring increase in gill NKA was less pronounced in smolts kept under sustained winter photoperiod and/or elevated temperature. Plasma thyroid hormone levels displayed day-night variations, which were affected by elevated temperature, either independently from photoperiod (decrease in T3 levels) or under natural photoperiod exclusively (increase in T4 nocturnal levels). Nocturnal MEL secretion was potentiated by the elevated temperature, which also altered the MEL profile under sustained winter photoperiod. Temperature also affected pineal MEL production in vitro, a response that depended on previous environmental acclimation of the organ. The results support the view that the salmon pineal is a photoperiod and temperature sensor, highlight the complexity of the interaction of these environmental factors on the endocrine system of S. salar, and indicate that climate change might compromise salmon's time "deciphering" during smoltification, downstream migration and seawater residence.
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Affiliation(s)
- Laura Gabriela Nisembaum
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins, BIOM, 66650, Banyuls-sur-Mer, France.
| | - Patrick Martin
- Conservatoire National du Saumon Sauvage, 43300, Chanteuges, France
| | - Michael Fuentes
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins, BIOM, 66650, Banyuls-sur-Mer, France
| | - Laurence Besseau
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins, BIOM, 66650, Banyuls-sur-Mer, France
| | - Elodie Magnanou
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins, BIOM, 66650, Banyuls-sur-Mer, France
| | - Stephen D McCormick
- S.O. Conte Anadromous Fish Research Laboratory, U.S. Geological Survey, Leetown Science Center, Turners Falls, MA, USA
| | - Jack Falcón
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins, BIOM, 66650, Banyuls-sur-Mer, France.,Biologie des Organismes et Ecosystèmes Aquatiques (BOREA) MNHN, CNRS 7208, UPMC, IRD 207, UCN, UA, Muséum National d'Histoire Naturelle, Paris Cedex, France
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Transcriptomic Analysis of Gill and Kidney from Asian Seabass ( Lates calcarifer) Acclimated to Different Salinities Reveals Pathways Involved with Euryhalinity. Genes (Basel) 2020; 11:genes11070733. [PMID: 32630108 PMCID: PMC7397140 DOI: 10.3390/genes11070733] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Revised: 06/29/2020] [Accepted: 06/29/2020] [Indexed: 12/13/2022] Open
Abstract
Asian seabass (or commonly known as barramundi), Lates calcarifer, is a bony euryhaline teleost from the Family Latidae, inhabiting nearshore, estuarine, and marine connected freshwaters throughout the tropical Indo-West Pacific region. The species is catadromous, whereby adults spawn in salinities between 28 and 34 ppt at the mouth of estuaries, with resultant juveniles usually moving into brackish and freshwater systems to mature, before returning to the sea to spawn again as adults. The species lives in both marine and freshwater habitats and can move quickly between the two; thus, the species' ability to tolerate changes in salinity makes it a good candidate for studying the salinity acclimation response in teleosts. In this study, the transcriptome of two major osmoregulatory organs (gills and kidneys) of young juvenile Asian seabass reared in freshwater and seawater were compared. The euryhaline nature of Asian seabass was found to be highly pliable and the moldability of the trait was further confirmed by histological analyses of gills and kidneys. Differences in major expression pathways were observed, with differentially expressed genes including those related to osmoregulation, tissue/organ morphogenesis, and cell volume regulation as central to the osmo-adaptive response. Additionally, genes coding for mucins were upregulated specifically under saline conditions, whereas several genes important for growth and development, as well as circadian entrainment were specifically enriched in fish reared in freshwater. Routing of the circadian rhythm mediated by salinity changes could be the initial step in salinity acclimation and possibly migration in euryhaline fish species such as the Asian seabass.
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Saha S, Singh KM, Gupta BBP. Melatonin synthesis and clock gene regulation in the pineal organ of teleost fish compared to mammals: Similarities and differences. Gen Comp Endocrinol 2019; 279:27-34. [PMID: 30026020 DOI: 10.1016/j.ygcen.2018.07.010] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2018] [Revised: 07/12/2018] [Accepted: 07/15/2018] [Indexed: 02/07/2023]
Abstract
The pineal organ of all vertebrates synthesizes and secretes melatonin in a rhythmic manner due to the circadian rhythm in the activity of arylalkylamine N-acetyltransferase (AANAT) - the rate-limiting enzyme in melatonin synthesis pathway. Nighttime increase in AANAT activity and melatonin synthesis depends on increased expression of aanat gene (a clock-controlled gene) and/or post-translation modification of AANAT protein. In mammalian and avian species, only one aanat gene is expressed. However, three aanat genes (aanat1a, aanat1b, and aanat2) are reported in fish species. While aanat1a and aanat1b genes are expressed in the fish retina, the nervous system and other peripheral tissues, aanat2 gene is expressed exclusively in the fish pineal organ. Clock genes form molecular components of the clockwork, which regulates clock-controlled genes like aanat gene. All core clock genes (i.e., clock, bmal1, per1, per2, per3, cry1 and cry2) and aanat2 gene (a clock-controlled gene) are expressed in the pineal organ of several fish species. There is a large body of information on regulation of clock genes, aanat gene and melatonin synthesis in the mammalian pineal gland. However, the information available on clock genes, aanat genes and melatonin synthesis in photoreceptive pineal organ of teleosts is fragmentary and not well documented. Therefore, we have reviewed published information on rhythmic expression of clock genes, aanat genes as well as synthesis of melatonin, and their regulation by photoperiod and temperature in teleostean pineal organ as compared to mammalian pineal gland. A critical analysis of the literature suggests that in contrast to the mammalian pineal gland, the pineal organ of teleosts (except salmonids) possesses a well developed indigenous clock composed of clock genes for regulation of rhythmic expression of aanat2 gene and melatonin synthesis. Further, the fish pineal organ also possesses essential molecular components for responding to light and temperature directly. The fish pineal organ seems to act as a potential master biological clock in most of the teleosts.
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Affiliation(s)
- Saurav Saha
- Environmental Endocrinology Laboratory, Department of Zoology, North-Eastern Hill University, Shillong 793022, India
| | - Kshetrimayum Manisana Singh
- Environmental Endocrinology Laboratory, Department of Zoology, North-Eastern Hill University, Shillong 793022, India
| | - Braj Bansh Prasad Gupta
- Environmental Endocrinology Laboratory, Department of Zoology, North-Eastern Hill University, Shillong 793022, India.
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Williams CR, Dittman AH, McElhany P, Busch DS, Maher M, Bammler TK, MacDonald JW, Gallagher EP. Elevated CO 2 impairs olfactory-mediated neural and behavioral responses and gene expression in ocean-phase coho salmon (Oncorhynchus kisutch). GLOBAL CHANGE BIOLOGY 2019; 25:963-977. [PMID: 30561876 PMCID: PMC7065673 DOI: 10.1111/gcb.14532] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2018] [Accepted: 11/06/2018] [Indexed: 05/16/2023]
Abstract
Elevated concentrations of CO2 in seawater can disrupt numerous sensory systems in marine fish. This is of particular concern for Pacific salmon because they rely on olfaction during all aspects of their life including during their homing migrations from the ocean back to their natal streams. We investigated the effects of elevated seawater CO2 on coho salmon (Oncorhynchus kisutch) olfactory-mediated behavior, neural signaling, and gene expression within the peripheral and central olfactory system. Ocean-phase coho salmon were exposed to three levels of CO2 , ranging from those currently found in ambient marine water to projected future levels. Juvenile coho salmon exposed to elevated CO2 levels for 2 weeks no longer avoided a skin extract odor that elicited avoidance responses in coho salmon maintained in ambient CO2 seawater. Exposure to these elevated CO2 levels did not alter odor signaling in the olfactory epithelium, but did induce significant changes in signaling within the olfactory bulb. RNA-Seq analysis of olfactory tissues revealed extensive disruption in expression of genes involved in neuronal signaling within the olfactory bulb of salmon exposed to elevated CO2 , with lesser impacts on gene expression in the olfactory rosettes. The disruption in olfactory bulb gene pathways included genes associated with GABA signaling and maintenance of ion balance within bulbar neurons. Our results indicate that ocean-phase coho salmon exposed to elevated CO2 can experience significant behavioral impairments likely driven by alteration in higher-order neural signal processing within the olfactory bulb. Our study demonstrates that anadromous fish such as salmon may share a sensitivity to rising CO2 levels with obligate marine species suggesting a more wide-scale ecological impact of ocean acidification.
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Affiliation(s)
- Chase R. Williams
- Department of Environmental and Occupational Health Sciences. University of Washington. Seattle, WA 98105
| | - Andrew H. Dittman
- Environmental and Fisheries Sciences Division, Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 2725 Montlake Blvd E Seattle WA 98112, USA
- Corresponding author at NOAA fisheries, Andrew H. Dittman, Ph.D., Tel: 206-860-3392,
| | - Paul McElhany
- Conservation Biology Division, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 802 Front Street, Mukilteo, WA 98275, USA
| | - D. Shallin Busch
- Conservation Biology Division, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 802 Front Street, Mukilteo, WA 98275, USA
- Ocean Acidification Program, Office of Oceanic and Atmospheric Research, National Oceanic and Atmospheric Administration, 2725 Montlake Blvd E, Seattle WA 98112, USA
| | - Michael Maher
- Conservation Biology Division, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 802 Front Street, Mukilteo, WA 98275, USA
| | - Theo K. Bammler
- Department of Environmental and Occupational Health Sciences. University of Washington. Seattle, WA 98105
| | - James W. MacDonald
- Department of Environmental and Occupational Health Sciences. University of Washington. Seattle, WA 98105
| | - Evan P. Gallagher
- Department of Environmental and Occupational Health Sciences. University of Washington. Seattle, WA 98105
- Corresponding author at the University of Washington, Evan P. Gallagher, Ph.D., Tel: 1-206-616-4739,
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Sánchez-Vázquez FJ, López-Olmeda JF, Vera LM, Migaud H, López-Patiño MA, Míguez JM. Environmental Cycles, Melatonin, and Circadian Control of Stress Response in Fish. Front Endocrinol (Lausanne) 2019; 10:279. [PMID: 31244768 PMCID: PMC6579845 DOI: 10.3389/fendo.2019.00279] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Accepted: 04/16/2019] [Indexed: 01/10/2023] Open
Abstract
Fish have evolved a biological clock to cope with environmental cycles, so they display circadian rhythms in most physiological functions including stress response. Photoperiodic information is transduced by the pineal organ into a rhythmic secretion of melatonin, which is released into the blood circulation with high concentrations at night and low during the day. The melatonin rhythmic profile is under the control of circadian clocks in most fish (except salmonids), and it is considered as an important output of the circadian system, thus modulating most daily behavioral and physiological rhythms. Lighting conditions (intensity and spectrum) change in the underwater environment and affect fish embryo and larvae development: constant light/darkness or red lights can lead to increased malformations and mortality, whereas blue light usually results in best hatching rates and growth performance in marine fish. Many factors display daily rhythms along the hypothalamus-pituitary-interrenal (HPI) axis that controls stress response in fish, including corticotropin-releasing hormone (Crh) and its binding protein (Crhbp), proopiomelanocortin A and B (Pomca and Pomcb), and plasma cortisol, glucose, and lactate. Many of these circadian rhythms are under the control of endogenous molecular clocks, which consist of self-sustained transcriptional-translational feedback loops involving the cyclic expression of circadian clock genes (clock, bmal, per, and cry) which persists under constant light or darkness. Exposing fish to a stressor can result in altered rhythms of most stress indicators, such as cortisol, glucose, and lactate among others, as well as daily rhythms of most behavioral and physiological functions. In addition, crh and pomca expression profiles can be affected by other factors such as light spectrum, which strongly influence the expression profile of growth-related (igf1a, igf2a) genes. Additionally, the daily cycle of water temperature (warmer at day and cooler at night) is another factor that has to be considered. The response to any acute stressor is not only species dependent, but also depends on the time of the day when the stress occurs: nocturnal species show higher responses when stressed during day time, whereas diurnal fish respond stronger at night. Melatonin administration in fish has sedative effects with a reduction in locomotor activity and cortisol levels, as well as reduced liver glycogen and dopaminergic and serotonergic activities within the hypothalamus. In this paper, we are reviewing the role of environmental cycles and biological clocks on the entrainment of daily rhythms in the HPI axis and stress responses in fish.
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Affiliation(s)
| | | | - Luisa Maria Vera
- Institute of Aquaculture, University of Stirling, Stirling, United Kingdom
| | - Herve Migaud
- Institute of Aquaculture, University of Stirling, Stirling, United Kingdom
| | - Marcos Antonio López-Patiño
- Laboratory Animal Physiology, Department Biology and Health Science, Faculty of Biology and Centro Singular de Investigación Mariña-ECIMAT, University of Vigo, Vigo, Spain
| | - Jesús M. Míguez
- Laboratory Animal Physiology, Department Biology and Health Science, Faculty of Biology and Centro Singular de Investigación Mariña-ECIMAT, University of Vigo, Vigo, Spain
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13
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Jarrold MD, Humphrey C, McCormick MI, Munday PL. Diel CO 2 cycles reduce severity of behavioural abnormalities in coral reef fish under ocean acidification. Sci Rep 2017; 7:10153. [PMID: 28860652 PMCID: PMC5578974 DOI: 10.1038/s41598-017-10378-y] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Accepted: 08/09/2017] [Indexed: 11/09/2022] Open
Abstract
Elevated CO2 levels associated with ocean acidification (OA) have been shown to alter behavioural responses in coral reef fishes. However, all studies to date have used stable pCO2 treatments, not considering the substantial diel pCO2 variation that occurs in shallow reef habitats. Here, we reared juvenile damselfish, Acanthochromis polyacanthus, and clownfish, Amphiprion percula, at stable and diel cycling pCO2 treatments in two experiments. As expected, absolute lateralization of A. polyacanthus and response to predator cue of Am. percula were negatively affected in fish reared at stable, elevated pCO2 in both experiments. However, diel pCO2 fluctuations reduced the negative effects of OA on behaviour. Importantly, in experiment two, behavioural abnormalities that were present in fish reared at stable 750 µatm CO2 were largely absent in fish reared at 750 ± 300 µatm CO2. Overall, we show that diel pCO2 cycles can substantially reduce the severity of behavioural abnormalities caused by elevated CO2. Thus, past studies may have over-estimated the impacts of OA on the behavioural performance of coral reef fishes. Furthermore, our results suggest that diel pCO2 cycles will delay the onset of behavioural abnormalities in natural populations.
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Affiliation(s)
- Michael D Jarrold
- College of Science and Engineering, James Cook University, Townsville, QLD 4811, Australia. .,ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, QLD 4811, Australia.
| | - Craig Humphrey
- National Sea Simulator, Australian Institute of Marine Science, PMB 3, Townsville, Queensland, 4810, Australia
| | - Mark I McCormick
- College of Science and Engineering, James Cook University, Townsville, QLD 4811, Australia.,ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, QLD 4811, Australia
| | - Philip L Munday
- ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, QLD 4811, Australia
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Cowan M, Azpeleta C, López-Olmeda JF. Rhythms in the endocrine system of fish: a review. J Comp Physiol B 2017; 187:1057-1089. [DOI: 10.1007/s00360-017-1094-5] [Citation(s) in RCA: 66] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2016] [Revised: 03/20/2017] [Accepted: 04/06/2017] [Indexed: 12/20/2022]
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15
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RNA-seq reveals differential gene expression in the brains of juvenile resident and migratory smolt rainbow trout (Oncorhynchus mykiss). COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY D-GENOMICS & PROTEOMICS 2016; 20:136-150. [DOI: 10.1016/j.cbd.2016.07.006] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2015] [Revised: 07/21/2016] [Accepted: 07/28/2016] [Indexed: 11/20/2022]
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16
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Adamska I, Lewczuk B, Markowska M, Majewski PM. Daily profiles of melatonin synthesis-related indoles in the pineal glands of young chickens (Gallus gallus domesticus L.). JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2016; 164:335-343. [DOI: 10.1016/j.jphotobiol.2016.10.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Revised: 09/30/2016] [Accepted: 10/03/2016] [Indexed: 11/16/2022]
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17
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Muñoz-Pérez JL, López-Patiño MA, Álvarez-Otero R, Gesto M, Soengas JL, Míguez JM. Characterization of melatonin synthesis in the gastrointestinal tract of rainbow trout (Oncorhynchus mykiss): distribution, relation with serotonin, daily rhythms and photoperiod regulation. J Comp Physiol B 2016; 186:471-84. [DOI: 10.1007/s00360-016-0966-4] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Revised: 01/22/2016] [Accepted: 01/25/2016] [Indexed: 10/22/2022]
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18
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Diurnal profiles of melatonin synthesis-related indoles, catecholamines and their metabolites in the duck pineal organ. Int J Mol Sci 2014; 15:12604-30. [PMID: 25032843 PMCID: PMC4139863 DOI: 10.3390/ijms150712604] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2014] [Revised: 07/01/2014] [Accepted: 07/03/2014] [Indexed: 11/17/2022] Open
Abstract
This study characterizes the diurnal profiles of ten melatonin synthesis-related indoles, the quantitative relations between these compounds, and daily variations in the contents of catecholamines and their metabolites in the domestic duck pineal organ. Fourteen-week-old birds, which were reared under a 12L:12D cycle, were killed at two-hour intervals. The indole contents were measured using HPLC with fluorescence detection, whereas the levels of catecholamines and their metabolites were measured using HPLC with electrochemical detection. All indole contents, except for tryptophan, showed significant diurnal variations. The 5-hydroxytryptophan level was approximately two-fold higher during the scotophase than during the photophase. The serotonin content increased during the first half of the photophase, remained elevated for approximately 10 h and then rapidly decreased in the middle of the scotophase. N-acetylserotonin showed the most prominent changes, with a more than 15-fold increase at night. The melatonin cycle demonstrated only an approximately 5-fold difference between the peak and nadir. The 5-methoxytryptamine content was markedly elevated during the scotophase. The 5-hydroxyindole acetic acid, 5-hydroxytryptophol, 5-methoxyindole acetic acid and 5-methoxytryptophol profiles were analogous to the serotonin rhythm. The norepinephrine and dopamine contents showed no significant changes. The DOPA, DOPAC and homovanillic acid levels were higher during the scotophase than during the photophase. Vanillylmandelic acid showed the opposite rhythm, with an elevated level during the daytime.
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19
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Gesto M, Soengas JL, Rodríguez-Illamola A, Míguez JM. Arginine vasotocin treatment induces a stress response and exerts a potent anorexigenic effect in rainbow trout, Oncorhynchus mykiss. J Neuroendocrinol 2014; 26:89-99. [PMID: 24341528 DOI: 10.1111/jne.12126] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Revised: 11/28/2013] [Accepted: 12/12/2013] [Indexed: 12/16/2022]
Abstract
The peptide arginine vasotocin (AVT), homologous to mammalian arginine vasopressin, is involved in many aspects of fish physiology, such as osmoregulation, regulation of biological rhythms, reproduction, metabolism or responses to stress, and the modulation of social behaviours. Because a decrease in appetite is a general response to stress in fish and other vertebrates, we investigated the role of AVT as a possible food intake regulator in fish. We used i.c.v. injections for central administration of AVT to rainbow trout (Oncorhynchus mykiss). In a first experiment, we evaluated the temporal response of food intake after AVT treatment. In a second experiment, we investigated the effects of central AVT administration on the response of typical stress markers (plasma cortisol, glucose and lactate), as well as brain serotonergic, noradrenergic and dopaminergic activity. In addition, the mRNA levels of genes involved in food intake regulation [neuropetide Y, pro-opiomelanocortin (POMC), cocaine- and amphetamine-regulated transcript (CART) and corticotrophin-releasing factor (CRF)] and in CRF- (CRF-binding protein) and AVT-signalling (pro-VT and AVT receptor), were also assessed after AVT treatment. Our results showed that AVT is a potent anorexigenic factor in fish. Increases of plasma cortisol and glucose after AVT treatment strongly suggest that AVT administration induced a stress response and that AVT action was mediated by hypothalamic-pituitary-interrenal axis activation, which was also supported by the increase of the serotonergic activity in trout telencephalon and hypothalamus. The increased hypothalamic levels of POMC and CART suggest that these peptides might have a role in the anorexigenic action of AVT, whereas the involvement of CRF signalling is unclear.
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Affiliation(s)
- M Gesto
- Laboratorio de Fisiología animal, Departamento de Biología Funcional y CC. de la Salud, Facultad de Biología, Universidade de Vigo, Vigo, Spain
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López-Patiño MA, Gesto M, Conde-Sieira M, Soengas JL, Míguez JM. Stress inhibition of melatonin synthesis in the pineal organ of rainbow trout (Oncorhynchus mykiss) is mediated by cortisol. ACTA ACUST UNITED AC 2014; 217:1407-16. [PMID: 24436377 DOI: 10.1242/jeb.087916] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Cortisol has been suggested to mediate the effect of stress on pineal melatonin synthesis in fish. Therefore, we aimed to determine how pineal melatonin synthesis is affected by exposing rainbow trout to different stressors, such as hypoxia, chasing and high stocking density. In addition, to test the hypothesis that cortisol is a mediator of such stress-induced effects, a set of animals were intraperitoneally implanted with coconut oil alone or containing cortisol (50 mg kg(-1) body mass) and sampled 5 or 48 h post-injection at midday and midnight. The specificity of such effect was also assessed in cultured pineal organs exposed to cortisol alone or with the general glucocorticoid receptor antagonist, mifepristone (RU486). Stress (in particular chasing and high stocking density) affected the patterns of plasma and pineal organ melatonin content during both day and night, with the greatest reduction occurring at night. The decrease in nocturnal melatonin levels in the pineal organ of stressed fish was accompanied by increased serotonin content and decreased AANAT2 enzymatic activity and mRNA abundance. Similar effects on pineal melatonin synthesis to those elicited by stress were observed in trout implanted with cortisol for either 5 or 48 h. These data indicate that stress negatively influences the synthesis of melatonin in the pineal organ, thus attenuating the day-night variations of circulating melatonin. The effect might be mediated by increased cortisol, which binds to trout pineal organ-specific glucocorticoid receptors to modulate melatonin rhythms. Our results in cultured pineal organs support this. Considering the role of melatonin in the synchronization of daily and annual rhythms, the results suggest that stress-induced alterations in melatonin synthesis could affect the availability of fish to integrate rhythmic environmental information.
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Affiliation(s)
- Marcos A López-Patiño
- Laboratorio de Fisioloxía Animal, Departamento de Bioloxía Funcional e Ciencias da Saúde, Facultade de Bioloxía, Universidade de Vigo, 36310 Vigo, Spain
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Dias C, Fagundes D, Gouveia Junior A, Silanes M, Oliveira J. Luz, Melatonina e Estresse Oxidativo na Piscicultura. BIOTA AMAZÔNIA 2013. [DOI: 10.18561/2179-5746/biotaamazonia.v3n3p169-176] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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Daily patterns of mRNA expression of two core circadian regulatory proteins, Clock2 and Per1, and two appetite-regulating peptides, OX and NPY, in goldfish (Carassius auratus). Comp Biochem Physiol A Mol Integr Physiol 2012; 163:127-36. [DOI: 10.1016/j.cbpa.2012.05.197] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2012] [Revised: 05/20/2012] [Accepted: 05/21/2012] [Indexed: 11/24/2022]
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Conde-Sieira M, Librán-Pérez M, López Patiño MA, Soengas JL, Míguez JM. Melatonin treatment alters glucosensing capacity and mRNA expression levels of peptides related to food intake control in rainbow trout hypothalamus. Gen Comp Endocrinol 2012; 178:131-8. [PMID: 22569117 DOI: 10.1016/j.ygcen.2012.04.011] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/15/2011] [Revised: 04/10/2012] [Accepted: 04/12/2012] [Indexed: 01/17/2023]
Abstract
As demonstrated in previous studies, the functioning of brain glucosensing systems in rainbow trout is altered under stress conditions in a way that they are unable to respond properly to changes in glucose levels. Melatonin has been postulated as necessary for homeostatic control of energy metabolism in several vertebrate groups, and in fish it has been suggested as an anti-stress molecule. To evaluate the possible effects of melatonin on glucosensing, we have incubated hypothalamus and hindbrains of rainbow trout at different glucose concentrations in the presence of increased doses (0.01, 1, and 100nM) of melatonin assessing whether or not the responses to changes in glucose levels of parameters related to glucosensing (glucose, glycogen and glucose 6-phosphate levels, activities of GK, GSase and PK, and mRNA content of GK, GLUT2, Kir6.x-like, and SUR-like) are modified in the presence of melatonin. While no effects of melatonin were observed in hindbrain, in hypothalamus melatonin treatment up-regulated glucosensing parameters, especially under hypo- and normo-glycaemic conditions. The effects of melatonin in hypothalamus occurred apparently through MT(1) receptors since most effects were counteracted by the presence of luzindole but not by the presence of 4-P-PDOT. Moreover, melatonin treatment induced in hypothalamus increased mRNA expression levels of NPY and decreased mRNA levels of POMC, CART, and CRF. A role of the hormone in daily re-adjustment of hypothalamic glucosensor machinery is discussed.
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Affiliation(s)
- Marta Conde-Sieira
- Laboratorio de Fisioloxía Animal, Departamento de Bioloxía Funcional e Ciencias da Saúde, Facultade de Bioloxía, Universidade de Vigo, Vigo, Spain
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