Publication: Influence of light intensity on plasma melatonin and locomotor activity rhythms in tench
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Date
2005
Authors
Vera, L.M. ; López Olmeda, J.F. ; Bayarri, M.J. ; Madrid, J.A. ; Sánchez Vázquez, F.J.
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Publisher
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DOI
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info:eu-repo/semantics/article
Description
©2005. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
This document is the Accepted version of a Published Work that appeared in final form in Chronobiology International: The Journal of Biological and Medical Rhythm Research.
Abstract
Melatonin production by the pineal organ is influenced by light intensity, as has been
described in most vertebrate species, in which melatonin is considered a synchronizer of
circadian rhythms. In the case of tench, strict nocturnal activity rhythms have been
described although the role of melatonin has not been clarified. In this study we
investigated daily activity and melatonin rhythms under 12:12 light-dark (LD)
conditions with two different light intensities (58.6 and 1091µW/cm2
), and the effect of
one hour broad spectrum white light pulses of different intensities (3.3, 5.3, 10.5,
1091.4 µW/cm2
) applied at mid darkness (MD) on nocturnal circulating melatonin. The
results showed that plasma melatonin in tench under LD 12:12 and high light conditions
displayed a rhythmic variation, where values at MD (255.8 ± 65.9 pg/ml) were higher
than at mid light (ML) (70.7 ± 31.9 pg/ml). Such a difference between MD and ML
values was reduced in animals exposed to LD 12:12 and low light intensity. The
application of one hour light pulses at MD lowered plasma melatonin to 111.6 ± 3.2
pg/ml (in the 3.3-10.5 µW/cm2 range) and to 61.8 ± 18.3 pg/ml (with the 1091.4
µW/cm2 light pulse) and totally suppressed nocturnal locomotor activity. These results
showed that melatonin rhythms persisted in tench exposed to low light intensity
although the amplitude of the rhythm is affected. In addition, it was observed that light
pulses applied at MD affected plasma melatonin content and locomotor activity. Such a
low threshold suggests that the melatonin system is capable of transducing light even
under dim conditions, which may be used by this nocturnal fish to synchronize to weak
night light signals (e.g. moonlight cycles)
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Citation
Chronobiology International
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