Ocular Melatonin Rhythms in Teleost Fish

Iigo, Masayuki; Furukawa, Kiyoshi; Nishi, Genjirou; Tabata, Mitsuo; Aida, Katsumi

doi:10.1159/000095200

Cited by 17 publications

(5 citation statements)

References 72 publications

(68 reference statements)

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“…It is generally believed that melatonin is produced by the photoreceptor cells in a circadian manner and that it acts as an autocrine and paracrine modulator of retinal function (Green and Besharse, 2004;Iuvone et al, 2005;Iigo et al, 2007). However, we have recently demonstrated that cells from the INL and GCL also expressed the enzymes of the melatonin synthesizing pathway, the arylalkylamine N-acetyltransferase (AANAT) and hydroxyindole-O-methyltransferase (HIOMT) in trout (Besseau et al, 2006) and seabass (unpublished) retinas.…”

Section: Discussionmentioning

confidence: 97%

Cloning and retinal expression of melatonin receptors in the European sea bass, Dicentrarchus labrax

Sauzet

Besseau

Pérez

et al. 2008

General and Comparative Endocrinology

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Melatonin contributes to synchronizing behaviors and physiological functions to daily and seasonal rhythm in fish. However, no coherent vision emerges because the effects vary with the species, sex, age, moment of the year or sexual cycle. And, scarce information is available concerning the melatonin receptors, which is crucial to our understanding of the role melatonin plays. We report here the full length cloning of three different melatonin receptor subtypes in the sea bass Dicentrarchus labrax, belonging, respectively, to the MT1, MT2 and Mel1c subtypes. MT1, the most abundantly expressed, was detected in the central nervous system, retina, and gills. MT2 was detected in the pituitary gland, blood cells and, to a lesser extend, in the optic tectum, diencephalon, liver and retina. Mel1c was mainly expressed in the skin; traces were found in the retina. The cellular sites of MT1 and MT2 expressions were investigated by in situ hybridization in the retina of pigmented and albino fish. The strongest signals were obtained with the MT1 riboprobes. Expression was seen in cells also known to express the enzymes of the melatonin biosynthesis, i.e., in the photoreceptor, inner nuclear and ganglion cell layers. MT1 receptor mRNAs were also abundant in the retinal pigment epithelium. The results are consistent with the idea that melatonin is an autocrine (neural retina) and paracrine (retinal pigment epithelium) regulator of retinal function. The molecular tools provided here will be of valuable interest to further investigate the targets and role of melatonin in nervous and peripheral tissues of fish.

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Section: Discussionmentioning

confidence: 97%

Cloning and retinal expression of melatonin receptors in the European sea bass, Dicentrarchus labrax

Sauzet

Besseau

Pérez

et al. 2008

General and Comparative Endocrinology

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“…Therefore, the pineal organ in fish could potentially be involved in mediating the effects of LD cycles on circadian locomotor activities [24,25,[31][32][33][34][35][36][37][38][39]. However, ocular melatonin rhythms in teleost fish, including the Japanese sea catfish, has been reported [40]. Thus, the pathways and organs involved in the entrainment of biological rhythms, and a site of circadian oscillator are unknown for the Japanese sea catfish.…”

Section: Discussionmentioning

confidence: 99%

Circadian locomotor activity in Japanese sea catfish Plotosus lineatus

2008

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To find out whether or not the locomotor activity of the Japanese sea catfish, Plotosus lineatus, shows a circadian rhythmicity, the locomotor activity of this catfish was recorded in a laboratory. All of the catfish recorded (n = 20) showed a nocturnal locomotor activity rhythm under a light-dark (LD) cycle (LD 12:12). The locomotor activity started after the light was turned off, and declined during the period of darkness. In five of the six catfish we examined, locomotor activity shifted gradually over the course of 3-4 days in order to synchronize to the LD cycle after it was advanced by 6 h. Locomotor activity persisted within a constant darkness (DD) in all eight of the catfish. The average free-running period of locomotor activity under DD lasted for 24.2 ± 0.4 h (mean ± SD). Thus, the present results demonstrate that the Japanese sea catfish has an endogenous circadian oscillator entrained by an LD cycle.

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“…In a number of teleost species, rhythmic melatonin production by both tissues is in phase (low during day and high at night) while in some other vertebrates (including teleosts), melatonin production in retina can be reversed thus being higher during the day than at night (Gern et al, 1978;Yu et al, 1981;Reiter et al, 1983;Serino et al, 1993;Iigo et al, 1997;Besseau et al, 2006;Iigo et al, 2007b). These phase shift patterns of secretion could be linked to differences within the melatonin biosynthesis pathway leading to the production of melatonin and more specifically arylalkylamine N-acetyltransferase (AANAT) which is the enzyme found in all vertebrates involved in the conversion of serotonin into melatonin (Klein et al, 1997).…”

Section: Introductionmentioning

confidence: 99%

Retinal light input is required to sustain plasma melatonin rhythms in Nile tilapia Oreochromis niloticus niloticus

Martinez-Chavez

Migaud

2009

Brain Research

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The aim of this work was to confirm previous findings suggesting that the eyes are required for night-time melatonin production in Nile tilapia and further characterise this divergent circadian organisation. To do so, melatonin levels were firstly measured in eyecups and plasma to determine circadian patterns of melatonin production.Secondly, the effect of partial ophthalmectomy on the suppression of melatonin production was determined in vivo as well as ex vivo pineal light/dark sensitivity.Finally, to investigate whether such findings could be related to post-surgery stress, melatonin analyses were performed in the subsequent 24 h and 7 days postophthalmectomy with cortisol levels assessed as an indicator of stress. Our results showed an inverse pattern of melatonin production in the eye cups of tilapia compared to blood circulating levels, suggesting different roles played by melatonin in these two tissues. Results then demonstrated that total or partial ophthalmectomy resulted in the suppression of night-time melatonin production. Furthermore, although pineals in culture were shown to be photosensitive, night-time melatonin levels were much lower than seen in other species. Finally, when performing sampling immediately or one week post-surgery, no difference in the melatonin profiles were observed. It is therefore unlikely that post-surgery stress would explain such suppression in melatonin production although all fish displayed high cortisol levels most probably due to social and handling stress. Taken together, these results provide further evidence of a new type of circadian organisation in a teleost species where the eyes are required to sustain night time melatonin levels. Section: Regulatory systems

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Ocular Melatonin Rhythms in Teleost Fish

Cited by 17 publications

References 72 publications

Cloning and retinal expression of melatonin receptors in the European sea bass, Dicentrarchus labrax

Cloning and retinal expression of melatonin receptors in the European sea bass, Dicentrarchus labrax

Circadian locomotor activity in Japanese sea catfish Plotosus lineatus

Retinal light input is required to sustain plasma melatonin rhythms in Nile tilapia Oreochromis niloticus niloticus

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