IMPORTANCE OF LIGHT IN TEMPORAL ORGANIZATION OF PHOTORECEPTOR PROTEINS AND MELATONIN-PRODUCING SYSTEM IN THE PINEAL OF CARP CATLA CATLA (original) (raw)
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Journal of experimental zoology. Part A, Ecological genetics and physiology, 2016
The tropical carp Catla catla is gaining importance for the studies of the impact of environmental changes on aquatic animals due to its surface dwelling habitat. To date, no information is available on the transcriptional profile of melatonin biosynthesizing enzyme genes in any tropical carp under either natural or artificial photothermal conditions in pineal and retina. The present study is an attempt to demonstrate the temporal pattern of expression of melatonin biosynthesizing enzyme genes, tryptophan hydroxylase 1 (tph1), arylalkylamine N-acetyltransferase (aanat1 and aanat2), and hydroxyindole-O-methyltransferase (hiomt) collectively and simultaneously in pineal organ and retina in tropical fish, C. catla, on a daily and seasonal basis under natural environmental conditions along with the serum melatonin levels. Depending upon the changes of the natural photothermal conditions, in four phases of an annual cycle, the variation and/or shifting of the rhythm parameters of differe...
Biological Rhythm Research, 2014
A temporal relationship between the daily and seasonal profiles of melatonin (N-acetyl-5-methoxytryptamine) in three different parts of gut, pineal, and serum as well as the density of arylalkylamine N-acetyltransferase (AANAT) protein, the key regulator of melatoninergic pathway in the pineal and respective regions of gut has been sought in a tropical carp Catla catla under natural photo-thermal conditions. The tissue samples were collected at four different clock hours in a daily cycle and the same was repeated in four different seasons in an annual cycle. In a daily cycle, concentrations of melatonin as well as the band intensity of a $23 kDa AANAT protein in each segment of gut, irrespective of sampling months, exhibited a peak at midday, while both the variables in the pineal and melatonin in serum showed a peak either in late dark phase (in March) or at midnight (in the remaining seasons). The simple correlation coefficient analysis of values revealed a negative correlation between the melatoninergic system in the gut and the pineal. Notably, seasonal fluctuations of photoperiod as well as water temperature exhibited a negative correlation with the daily peak values of pineal and serum melatonin, but no significant correlation with the respective values of gut melatonin. In conclusion, attainment of a daily peak in melatonin in the gut, unlike in the pineal and serum, does not seem to be a dark-dependent phenomenon.
Biological Rhythm Research, 2014
The daily profiles of melatonin and arylalkylamine N-acetyltransferase (AANAT) protein, the key enzyme of the melatoninergic pathway, in three anatomical segments of gut were studied in carp which were held under natural (NP) or long (LP; LD 16:08) or short (SP; LD 08:16) photoperiods or continuous light (LL; LD 24:00) or continuous darkness (DD; LD 00:24) for 30 days. The levels of melatonin and the density of a~23 kDa AANAT protein, in each gut segment, exhibited a daily rhythm with a peak at midday, irrespective of LD regimens to which the carp were held. None of the photo schedules had any significant effects on mesor values of gut melatonin and AANAT. However, compared to the rhythm features in NP fish, a significant reduction in the amplitude and a significant phase delay in the midday peak, as depicted by the value of acrophase (Ø), were noted in the gut of SP and DD carp. Collectively, it appears reasonable to argue that environmental lighting conditions may not be the synchronizer of daily periodicity in gut melatoninergic system, though the secondary effects of available light in determining its rhythm features in carp may not be ignored.
Journal of Neuroendocrinology, 2003
Complete melatonin rhythm generating systems, including photodetector, circadian clock and melatonin synthesis machinery, are located within individual photoreceptor cells in two sites in Teleost fish: the pineal organ and retina. In both, light regulates daily variations in melatonin secretion by controlling the activity of arylalkylamine N-acetyltransferase (AANAT). However, in each species examined to date, marked differences exist between the two organs which may involve the genes encoding the photopigments, genes encoding AANAT, the times of day at which AANAT activity and melatonin production peak and the developmental schedule. We review the fish pineal and retinal melatonin rhythm generating systems and consider the evolutional pressures and other factors which led to these differences.
Marine Genomics, 2013
The goldlined spinefoot, Siganus guttatus, is a lunar-synchronized spawner, which repeatedly releases gametes around the first quarter moon during the reproductive season. A previous study reported that manipulating moonlight brightness at night disrupted synchronized spawning, suggesting involvement of this natural light source in lunar synchronization. The present study examined whether the mRNA expression pattern of melatonin receptor subtypes MT1 and Mel 1c in the pineal organ of the goldlined spinefoot is related to moonlight. Realtime quantitative polymerase chain reaction analysis revealed that the abundance of MT1 and Mel 1c mRNA at midnight increased during the new moon phase and decreased during the full moon phase. Exposing fish to moonlight intensity during the full moon period resulted in a decrease in Mel 1c mRNA abundance within 1 h. Fluctuations in the melatonin receptor genes according to changes in the moon phase agreed with those of melatonin levels in the blood. These results indicate that periodic changes in cues from the moon influence melatonin receptor mRNA expression levels. The melatonin-melatonin receptor system may play a role in predicting the moon phase through changes in night brightness.
A B S T R A C T Arylalkylamine N-acetyltransferase (AANAT) activity, aanat gene expression and melatonin production have been reported to exhibit prominent circadian rhythm in the pineal organ of most species of fish. Three types of aanat genes are expressed in fish, but the fish pineal organ predominantly expresses aanat2 gene. Increase and decrease in daylength is invariably associated with increase and decrease in temperature, respectively. But so far no attempt has been made to delineate the role of photoperiod and temperature in regulation of the circadian rhythm of aanat2 gene expression in the pineal organ of any fish with special reference to seasons. Therefore, we studied effects of various lighting regimes (12L-12D, 16L-8D, 8L-16D, LL and DD) at a constant temperature (25 °C) and effects of different temperatures (15°, 25° and 35 °C) under a common photoperiod 12L-12D on circadian rhythm of aanat2 gene expression in the pineal organ of Clarias gariepinus during summer and winter seasons. Aanat2 gene expression in fish pineal organ was studied by measuring aanat2 mRNA levels using Real-Time PCR. Our findings indicate that the pineal organ of C. gariepinus exhibits a prominent circadian rhythm of aanat2 gene expression irrespective of photoperiods, temperatures and seasons, and the circadian rhythm of aanat2 gene expression responds differently to different photoperiods and temperatures in a season-dependent manner. Existence of circadian rhythm of aanat2 gene expression in pineal organs maintained in vitro under 12L-12D and DD conditions as well as a free running rhythm of the gene expression in pineal organ of the fish maintained under LL and DD conditions suggest that the fish pineal organ possesses an endogenous circadian oscillator, which is entrained by light-dark cycle.
Cell and Tissue Research, 1991
The levels of melatonin and the activities of two enzymes of the melatonin biosynthetic pathway, serotonin N-acetyltransferase (NAT) and hydroxyindole-O-methyltransferase (HIOMT), were measured throughout the light-dark cycle in the retina of a teleost fish, the pike. HIOMT activity did not display significant variations, whereas NAT activity and melatonin content showed a daily rhythm, high levels occurring during the night. The profiles of the latter two rhythms did not closely match one another and differed from those previously described in the pineal organ of the same species. These results are discussed with respect to a possible paracrine role of retinal melatonin. Melatonin-like immunoreactivity was found in the photoreceptor cell layer and in the Müller cells of the inner nuclear layer. The intensity of the melatonin-like immunoreactivity varied throughout the 24 h light-dark cycle, in good correlation with the variations in the melatonin level as measured by radioimmunoassay.
Journal of Comparative Physiology A, 1990
Hormonal and neural signals transmitted from the pineal organ to the brain in cold-blooded vertebrates presumably convert information about the ambient illumination into signals which may be used to mediate photoperiodic and circadian responses. The possible intrapineal function of melatonin was investigated by recording intra-and extracellularly from photoreceptors and second-order neurons in the isolated superfused pineal organ of the trout (Salmo gairdneri). Melatonin added through the perfusion bath to the explanted pineal organ caused a dose-related and reversible inhibition of ganglion cells of the luminance type whereas the hormone did not significantly affect the membrane potential of photoreceptors and their light-evoked response. The observed effects seem to be independent from photoperiod and adaptation conditions. These results suggest that melatonin provides a feedforward signal to intrapineal neurons regulating the neural output of the organ.