Reppert SM, Weaver DR, Cassone VM, et al. Melatonin receptor are for the birds: molecular analysis of two receptor subtypes differentially expressed in chick brain. Neuron 15: 1003-15

Laboratory of Developmental Chronobiology, Massachusetts General Hospital, Harvard Medical School, Boston 02114, USA.
Neuron (Impact Factor: 15.05). 12/1995; 15(5):1003-15. DOI: 10.1016/0896-6273(95)90090-X
Source: PubMed


Two receptors (CKA and CKB) of the G protein-coupled melatonin receptor family were cloned from chick brain. CKA encodes a protein that is 80% identical at the amino acid level to the human Mel1a melatonin receptor and is thus designated the chick Mel1a melatonin receptor. CKB encodes a protein that is 80% identical to the Xenopus melatonin receptor and defines a new receptor subtype, the Mel1c melatonin receptor, which is distinct from the Mel1a and Mel1b melatonin receptor subtypes. A melatonin receptor family consisting of three subtypes is supported by PCR cloning of distinct melatonin receptor fragments from Xenopus and zebrafish. Expression of CKA and CKB results in similar ligand binding and functional characteristics. The widespread distribution of CKA and CKB mRNA in brain provides a molecular substrate for the profound actions of melatonin in birds.

1 Follower
39 Reads
  • Source
    • "Melatonin may have direct and indirect effects. Most of the avian brain is sensitive to melatonin, as shown by the widespread distribution of melatonin receptors in almost all brain regions of several birds species [44-46] including Sylvia warblers (Fusani & Gahr, unpublished). Thus, it is conceivable the melatonin acts directly on some area to suppress (or reduce) Zugunruhe by influencing circadian oscillators [5,47]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: A remarkable aspect of bird migration is its nocturnality, particularly common in Passeriformes. The switch in activity from purely diurnal to also nocturnal is evident even in caged birds that during migratory periods develop an intense nocturnal restlessness, termed Zugunruhe. The mechanisms that control this major change in activity are mostly unknown. Previous work with Sylvia warblers suggested an involvement of melatonin, a hormone associated with day-night cycles in most vertebrates. In a recent study we found no effects of melatonin administration on Zugunruhe during spring migration. However, previous studies indicated that the response to melatonin manipulation could differ between spring and autumn migration, which are in fact separate life history stages. Here we tested whether a non-invasive treatment with melatonin can alter Zugunruhe in wild garden warblers S. borin and blackcaps S. atricapilla subject to temporary captivity at an autumnal stopover site. Food availability in the cage (yes/no) was added as a second factor because previous work showed that it enhanced Zugunruhe. The melatonin treatment significantly decreased the amount of Zugunruhe, while the availability of food only tended to increase the amount of Zugunruhe. Fuel deposits also had a strong effect on the amount of nocturnal activity: lean birds with a fat score of 1 showed significantly less Zugunruhe than fatter birds. The change in body mass during the time spent in the recording cage depended on food availability, but not on any of the other factors. This study shows that the migratory programme of two Sylvia warblers can be manipulated by administration of exogenous melatonin and confirms that this hormone is involved in the control of migratory behaviour. To our knowledge, this is one of the first demonstrations that the autumn migratory programme can be altered by hormonal manipulation in migrating birds. The comparison with a similar study carried out with the same modalities during spring migration suggests that there are seasonal differences in the sensitivity of the migratory programme to hormonal factors. In birds breeding in the northern hemisphere, the importance of a timely arrival to the breeding sites could explain why the control of the migratory programme is more rigid in spring.
    Frontiers in Zoology 12/2013; 10(1):79. DOI:10.1186/1742-9994-10-79 · 3.05 Impact Factor
  • Source
    • "The vSCN, but not the mSCN, expresses metabolic and electrical rhythmicity and receives retinohypothalamic (RHT) input. Further, the vSCN, but not the mSCN, contains melatonin receptor binding (Cassone et al., 1995; Lu and Cassone, 1993; Reppert et al., 1995; Rivkees et al., 1989), and exogenous melatonin inhibits metabolic activity in the vSCN (Lu and Cassone, 1993) but not in the mSCN. Finally , light activates c-fos expression in the vSCN, but not in the mSCN (King and Follett, 1997). "
    [Show abstract] [Hide abstract]
    ABSTRACT: In birds, biological clock function pervades all aspects of biology, controlling daily changes in sleep: wake, visual function, song, migratory patterns and orientation, as well as seasonal patterns of reproduction, song and migration. The molecular bases for circadian clocks are highly conserved, and it is likely the avian molecular mechanisms are similar to those expressed in mammals, including humans. The central pacemakers in the avian pineal gland, retinae and SCN dynamically interact to maintain stable phase relationships and then influence downstream rhythms through entrainment of peripheral oscillators in the brain controlling behavior and peripheral tissues. Birds represent an excellent model for the role played by biological clocks in human neurobiology; unlike most rodent models, they are diurnal, they exhibit cognitively complex social interactions, and their circadian clocks are more sensitive to the hormone melatonin than are those of nocturnal rodents.
    Frontiers in Neuroendocrinology 10/2013; 35(1). DOI:10.1016/j.yfrne.2013.10.002 · 7.04 Impact Factor
  • Source
    • "These are G-protein-coupled receptors (GPCRs) (Reppert et al., 1995). Mel1a and Mel1c receptors are present in the LHRN (visual SCN) in the chicken brain (Reppert et al., 1995). Contrary to the melatonin rhythm, which is higher in the scotophase (dark period), [125I]-iodomelatonin binding in the brain is higher during the photophase and lower during the scotophase in chicken (Yuan and Pang, 1992), quail (Yuan and Pang, 1990), and pigeon (Yuan and Pang, 1991). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Seasonally breeding birds detect environmental signals, such as light, temperature, food availability, and presence of mates to time reproduction. Hypothalamic neurons integrate external and internal signals, and regulate reproduction by releasing neurohormones to the pituitary gland. The pituitary gland synthesizes and releases gonadotropins which in turn act on the gonads to stimulate gametogenesis and sex steroid secretion. Accordingly, how gonadotropin secretion is controlled by the hypothalamus is key to our understanding of the mechanisms of seasonal reproduction. A hypothalamic neuropeptide, gonadotropin-releasing hormone (GnRH), activates reproduction by stimulating gonadotropin synthesis and release. Another hypothalamic neuropeptide, gonadotropin-inhibitory hormone (GnIH), inhibits gonadotropin synthesis and release directly by acting on the pituitary gland or indirectly by decreasing the activity of GnRH neurons. Therefore, the next step to understand seasonal reproduction is to investigate how the activities of GnRH and GnIH neurons in the hypothalamus and their receptors in the pituitary gland are regulated by external and internal signals. It is possible that locally-produced triiodothyronine resulting from the action of type 2 iodothyronine deiodinase on thyroxine stimulates the release of gonadotropins, perhaps by action on GnRH neurons. The function of GnRH neurons is also regulated by transcription of the GnRH gene. Melatonin, a nocturnal hormone, stimulates the synthesis and release of GnIH and GnIH may therefore regulate a daily rhythm of gonadotropin secretion. GnIH may also temporally suppress gonadotropin secretion when environmental conditions are unfavorable. Environmental and social milieus fluctuate seasonally in the wild. Accordingly, complex interactions of various neuronal and hormonal systems need to be considered if we are to understand the mechanisms underlying seasonal reproduction.
    Frontiers in Neuroscience 03/2013; 7:38. DOI:10.3389/fnins.2013.00038 · 3.66 Impact Factor
Show more