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ABSTRACT: Recent studies on several fish species, especially carp, implicated pineal hormone melatonin (N-acetyl-5-methoxytryptamine) as a potent candidate in the regulatory mechanism of seasonal reproduction. Under natural conditions, the temporal pattern of serum melatonin varied with daily light-dark cycle and the reproductive status of the fish as well. Carefully controlled study revealed that exogenous administration of melatonin may result in stimulation or inhibition or no influences at all on the gonadal functions depending on the reproductive status of fish. Cross-talk between the melatonin and ovarian steroid has been evident from in vitro study, in which melatonin accelerated the action of 17α,20β-dihydroxy-4-pregnen-3-one or maturation inducing hormone (MIH) on meiotic cell cycle resumption in carp oocytes by formation of maturation promoting factor (MPF) - a complex of two proteins, cyclin B and cyclin dependant kinase Cdk1. While several lines of evidence suggest melatonin effects on hypothalamo-hypophyseal-gonadal axis, localization and dynamics of a 37-kDa melatonin receptor protein in carp oocytes argued in favor of extra-hypothalamic direct action of melatonin on fish reproduction. A recent study in carp indicated that influences of an identical regimen of photoperiods in different parts of annual cycle on ovarian functions vary in relation to the profiles of serum melatonin, but not to any rhythm parameters of MT1 or MT2 receptors on the gonad or brain. The purpose of this short review is to bring together the current knowledge on the biological effects of melatonin on fish reproduction mainly focusing the recent findings on carp.
General and Comparative Endocrinology 10/2012; · 3.27 Impact Factor
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ABSTRACT: Previously, we showed that rhinovirus (RV), which is responsible for the majority of common colds, disrupts airway epithelial barrier function, as evidenced by reduced transepithelial resistance (R(T)), dissociation of zona occludins 1 (ZO-1) from the tight junction complex, and bacterial transmigration across polarized cells. We also showed that RV replication is required for barrier function disruption. However, the underlying biochemical mechanisms are not known. In the present study, we found that a double-stranded RNA (dsRNA) mimetic, poly(I:C), induced tight junction breakdown and facilitated bacterial transmigration across polarized airway epithelial cells, similar to the case with RV. We also found that RV and poly(I:C) each stimulated Rac1 activation, reactive oxygen species (ROS) generation, and Rac1-dependent NADPH oxidase 1 (NOX1) activity. Inhibitors of Rac1 (NSC23766), NOX (diphenylene iodonium), and NOX1 (small interfering RNA [siRNA]) each blocked the disruptive effects of RV and poly(I:C) on R(T), as well as the dissociation of ZO-1 and occludin from the tight junction complex. Finally, we found that Toll-like receptor 3 (TLR3) is not required for either poly(I:C)- or RV-induced reductions in R(T). Based on these results, we concluded that Rac1-dependent NOX1 activity is required for RV- or poly(I:C)-induced ROS generation, which in turn disrupts the barrier function of polarized airway epithelia. Furthermore, these data suggest that dsRNA generated during RV replication is sufficient to disrupt barrier function.
Journal of Virology 07/2011; 85(13):6795-808. · 5.40 Impact Factor
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Shyamala Ganesan,
Andrea N Faris,
Adam T Comstock,
Sangbrita S Chattoraj, Asamanja Chattoraj,
John R Burgess,
Jeffrey L Curtis,
Fernando J Martinez,
Suzanna Zick,
Marc B Hershenson,
Uma S Sajjan
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ABSTRACT: Chronic obstructive pulmonary disease (COPD) is characterized by chronic bronchitis, emphysema and irreversible airflow limitation. These changes are thought to be due to oxidative stress and an imbalance of proteases and antiproteases. Quercetin, a plant flavonoid, is a potent antioxidant and anti-inflammatory agent. We hypothesized that quercetin reduces lung inflammation and improves lung function in elastase/lipopolysaccharide (LPS)-exposed mice which show typical features of COPD, including airways inflammation, goblet cell metaplasia, and emphysema.
Mice treated with elastase and LPS once a week for 4 weeks were subsequently administered 0.5 mg of quercetin dihydrate or 50% propylene glycol (vehicle) by gavage for 10 days. Lungs were examined for elastance, oxidative stress, inflammation, and matrix metalloproteinase (MMP) activity. Effects of quercetin on MMP transcription and activity were examined in LPS-exposed murine macrophages.
Quercetin-treated, elastase/LPS-exposed mice showed improved elastic recoil and decreased alveolar chord length compared to vehicle-treated controls. Quercetin-treated mice showed decreased levels of thiobarbituric acid reactive substances, a measure of lipid peroxidation caused by oxidative stress. Quercetin also reduced lung inflammation, goblet cell metaplasia, and mRNA expression of pro-inflammatory cytokines and muc5AC. Quercetin treatment decreased the expression and activity of MMP9 and MMP12 in vivo and in vitro, while increasing expression of the histone deacetylase Sirt-1 and suppressing MMP promoter H4 acetylation. Finally, co-treatment with the Sirt-1 inhibitor sirtinol blocked the effects of quercetin on the lung phenotype.
Quercetin prevents progression of emphysema in elastase/LPS-treated mice by reducing oxidative stress, lung inflammation and expression of MMP9 and MMP12.
Respiratory research 09/2010; 11:131. · 3.36 Impact Factor
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Shyamala Ganesan,
Andrea Faris,
Adam Comstock,
Sangbrita Chattoraj, Asamanja Chattoraj,
John Burgess,
Jeffrey Curtis,
Fernando Martinez,
Suzanna Zick,
Marc Hershenson,
Uma Sajjan
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ABSTRACT: Abstract Background Chronic obstructive pulmonary disease (COPD) is characterized by chronic bronchitis, emphysema and irreversible airflow limitation. These changes are thought to be due to oxidative stress and an imbalance of proteases and antiproteases. Quercetin, a plant flavonoid, is a potent antioxidant and anti-inflammatory agent. We hypothesized that quercetin reduces lung inflammation and improves lung function in elastase/lipopolysaccharide (LPS)-exposed mice which show typical features of COPD, including airways inflammation, goblet cell metaplasia, and emphysema. Methods Mice treated with elastase and LPS once a week for 4 weeks were subsequently administered 0.5 mg of quercetin dihydrate or 50% propylene glycol (vehicle) by gavage for 10 days. Lungs were examined for elastance, oxidative stress, inflammation, and matrix metalloproteinase (MMP) activity. Effects of quercetin on MMP transcription and activity were examined in LPS-exposed murine macrophages. Results Quercetin-treated, elastase/LPS-exposed mice showed improved elastic recoil and decreased alveolar chord length compared to vehicle-treated controls. Quercetin-treated mice showed decreased levels of thiobarbituric acid reactive substances, a measure of lipid peroxidation caused by oxidative stress. Quercetin also reduced lung inflammation, goblet cell metaplasia, and mRNA expression of pro-inflammatory cytokines and muc5AC. Quercetin treatment decreased the expression and activity of MMP9 and MMP12 in vivo and in vitro, while increasing expression of the histone deacetylase Sirt-1 and suppressing MMP promoter H4 acetylation. Finally, co-treatment with the Sirt-1 inhibitor sirtinol blocked the effects of quercetin on the lung phenotype. Conclusions Quercetin prevents progression of emphysema in elastase/LPS-treated mice by reducing oxidative stress, lung inflammation and expression of MMP9 and MMP12.
Respiratory Research. 01/2010;
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ABSTRACT: Melatonin is a hormone secreted from the pineal gland specifically at night and contributes to a wide array of physiological functions in mammals. Melatonin is one of the most well understood output of the circadian clock located in the suprachiasmatic nucleus. Melatonin synthesis is controlled distally via the circadian clock located in the suprachiasmatic nucleus and proximally regulated by norepinephrine released in response to the circadian clock signals. To understand melatonin synthesis in vivo, we have performed microdialysis analysis of the pineal gland, which monitors melatonin as well as the precursor (serotonin) and intermediate (N-acetylserotonin) of melatonin synthesis in freely moving animals in realtime at high resolution. Our data revealed a number of novel features of melatonin production undetected using conventional techniques, which include (1) large inter-individual variations of melatonin onset timing; (2) circadian regulation of serotonin synthesis and secretion in the pineal gland; and (3) a revised view on the rate-limiting step of melatonin formation in vivo. This article will summarize the main findings from our laboratory regarding melatonin formation in mammals.
Reviews in Endocrine and Metabolic Disorders 12/2009; 10(4):237-43. · 3.17 Impact Factor
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ABSTRACT: Small laboratory animals have provided significant information about melatonin regulation, yet most of these organisms are nocturnal and regulate melatonin synthesis by mechanisms that diverge from those of humans. For example, in all rodents examined, melatonin secretion occurs with a time lag of several hours after the onset of darkness; in addition, arylalkylamine N-acetyltransferase (AANAT), the key enzyme in melatonin synthesis, displays dynamic transcriptional activation specifically at night in all rodents studied to date. In ungulates and primates including humans, on the other hand, melatonin secretion occurs immediately during the early night and is controlled by circadian posttranscriptional regulation of AANAT. We hypothesize that the diurnal Octodon degus (an Hystricognath rodent) could serve as an improved experimental model for studies of human melatonin regulation. To test this, we monitored melatonin production in degus using pineal microdialysis and characterized the regulation of melatonin synthesis by analyzing degu Aanat. Degu pineal melatonin rises with little latency at night, as in ungulates and primates. In addition, degu Aanat mRNA expression displays no detectable diurnal variation, suggesting that, like ungulates and primates, melatonin in this species is regulated by a posttranscriptional mechanism. Compared with AANAT from all rodents examined to date, the predicted amino acid sequence of degu AANAT is phylogenetically more closely related to ungulate and primate AANAT. These data suggest that Octodon degus may provide an ideal model system for laboratory investigation of mechanisms of melatonin synthesis and secretion in diurnal mammals.
Journal of Pineal Research 07/2009; 47(1):75-81. · 5.79 Impact Factor
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ABSTRACT: We studied the localization, sub-cellular distribution and daily rhythms of a 37 kDa melatonin receptor (Mel(1a)R) in the ovary to assess its temporal relationship with the serum melatonin levels in four different reproductive phases in carp Catla catla. Our immunocytochemical study accompanied by Western blot analysis of Mel(1a)R in the ovary revealed that the expression of this 37-kDa protein was greater in the membrane fraction than in the cytosol. Ovarian Mel(1a)R protein peaked at midnight and fell at midday in each reproductive phase. Conversely, serum melatonin levels in the same fish demonstrated a minimum diurnal value at midday in all seasons, but a peak at midnight (during pre-spawning, spawning, and post-spawning phases) or at late dark phase (during preparatory phase). In an annual cycle, band intensity of Mel(1a)R protein showed a maximum at night in the spawning phase and a minimum in the post-spawning phase, demonstrating an inverse relationship with the levels of serum melatonin. Our data provide first evidence of the presence of Mel(1a) melatonin receptor in carp ovary and offer interesting perspectives especially for the study of the mechanisms of the control of its rhythmicity and its response to external factors.
Comparative biochemistry and physiology. Part A, Molecular & integrative physiology 12/2008; 152(3):327-33. · 2.20 Impact Factor
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ABSTRACT: Serotonin (5-hydroxytryptamine, 5-HT), a precursor for melatonin production, is produced abundantly in the pineal gland of all vertebrate animals. The synthesis of 5-HT in the pineal gland is rate limited by tryptophan hydroxylase 1 (TPH1) whose activity displays a twofold increase at night. Earlier studies from our laboratory demonstrate that pineal 5-HT secretion exhibits dynamic circadian rhythms with elevated levels during the early night, and that the increase is controlled by adrenergic signaling at night. In this study, we report that (a) 5-HT total output from the pineal gland and TPH1 protein levels both display diurnal rhythms with a twofold increase at night; (b) stimulation of cAMP signaling elevates 5-HT output in vivo; (c) 5-HT total output and TPH1 protein content in rat pineal gland are both acutely inhibited by light exposure at night. Consistent with these findings, molecular analysis of TPH1 protein revealed that (a) TPH1 is phosphorylated at the serine 58 in vitro and in the night pineal gland; and (b) phosphorylation of TPH1 at this residue is required for cAMP-enhanced TPH1 protein stability. These data support the model that increased nocturnal 5-HT synthesis in the pineal gland is mediated by the phosphorylation of TPH1 at the serine 58, which elevates the TPH1 protein content and activity at night.
Journal of Pineal Research 09/2008; 45(4):506-14. · 5.79 Impact Factor
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ABSTRACT: The influences of serotonin (5-hydroxytryptamine) on the action of melatonin (N-acetyl-5-methoxytryptamine) in MIH (maturation inducing hormone)-induced meiotic resumption were evaluated in the oocytes of carp Catla catla using an in vitro model. Oocytes from gravid female carp were isolated and incubated separately in Medium 199 containing either (a) only melatonin (MEL; 100 pg/mL), or (b) only serotonin (SER; 100 pg/mL), or (c) only MIH (1 microg/mL), or (d) MEL and MIH (e) or MEL (4 h before) and MIH, or (f) MEL and SER, (g) or SER and MIH, or (h) SER (4 h before) and MIH, or (i) luzindole (L-antagonist of MEL receptors; 10 microM) and MEL, or (j) MEL, L and MIH, or (k) MEL (4 h before), L and MIH, or (l) metoclopramide hydrochloride (M-antagonist of SER receptors; 10 microM) and SER, or (m) M, MEL, SER, or (n) M, SER and MIH, or (o) M, SER (4 h before) and MIH, or (p) M, MEL SER and MIH, or (q) MEL, L, SER and M, or (r) MEL, L, SER, M, and MIH, or (s) MEL, SER, L and MIH. Control oocytes were incubated in the medium alone. Oocytes were incubated for 4, or 8, or 12, or 16 h and effects were evaluated by considering the rate (%) of germinal vesicle breakdown (GVBD). At the end of 16 h incubation, 93.24+/-1.57% oocytes underwent GVBD following incubation with only MIH, while incubation with only MEL or only SER resulted in 77.15+/-1.91% or 14.42+/-0.43% GVBD respectively. Interestingly, incubation with MEL 4 h prior to addition of MIH in the medium, led to an accelerated rate of GVBD (92.58+/-1.10% at 12 h). In contrast, SER, irrespective of its time of application in relation to MIH, resulted in a maximum of 64.57+/-0.86% GVBD. While L was found to reduce the stimulatory actions of melatonin, M suppressed the inhibitory actions of serotonin. In each case, both electrophoretic and immunoblot studies revealed that the rate of GVBD was associated with the rate of formation of maturation promoting factor (a complex of two proteins: a regulatory component--cyclin B and the catalytic component--Cdk1 or cdc2). Collectively, the present study reports for the first time that SER not only inhibits the independent actions of MIH, but also the actions of MEL on the MIH-induced oocytes maturation in carp.
Comparative biochemistry and physiology. Part A, Molecular & integrative physiology 08/2008; 150(3):301-6. · 2.20 Impact Factor
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ABSTRACT: The influences of serotonin (5-hydroxytryptamine) on the action of melatonin (N-acetyl-5-methoxytrypta-mine) in MIH (maturation inducing hormone)-induced meiotic resumption were evaluated in the oocytes of carp Catla catla using an in vitro model. Oocytes from gravid female carp were isolated and incubated separately in Medium 199 containing either (a) only melatonin (MEL; 100 pg/mL), or (b) only serotonin (SER; 100 pg/mL), or (c) only MIH (1 μg/mL), or (d) MEL and MIH (e) or MEL (4 h before) and MIH, or (f) MEL and SER, (g) or SER and MIH, or (h) SER (4 h before) and MIH, or (i) luzindole (L-antagonist of MEL receptors; 10 μM) and MEL, or (j) MEL, L and MIH, or (k) MEL (4 h before), L and MIH, or (l) metoclopramide hydrochloride (M-antagonist of SER receptors; 10 μM) and SER, or (m) M, MEL, SER, or (n) M, SER and MIH, or (o) M, SER (4 h before) and MIH, or (p) M, MEL SER and MIH, or (q) MEL, L, SER and M, or (r) MEL, L, SER, M, and MIH, or (s) MEL, SER, L and MIH. Control oocytes were incubated in the medium alone. Oocytes were incubated for 4, or 8, or 12, or 16 h and effects were evaluated by considering the rate (%) of germinal vesicle breakdown (GVBD). At the end of 16 h incubation, 93.24 ± 1.57% oocytes underwent GVBD following incubation with only MIH, while incubation with only MEL or only SER resulted in 77.15 ± 1.91% or 14.42 ± 0.43% GVBD respectively. Interestingly, incubation with MEL 4 h prior to addition of MIH in the medium, led to an accelerated rate of GVBD (92.58 ± 1.10% at 12 h). In contrast, SER, irrespective of its time of application in relation to MIH, resulted in a maximum of 64.57 ± 0.86% GVBD. While L was found to reduce the stimulatory actions of melatonin, M suppressed the inhibitory actions of serotonin. In each case, both electrophoretic and immunoblot studies revealed that the rate of GVBD was associated with the rate of formation of maturation promoting factor (a complex of two proteins: a regulatory component – cyclin B and the catalytic component – Cdk1 or cdc2). Collectively, the present study reports for the first time that SER not only inhibits the independent actions of MIH, but also the actions of MEL on the MIH-induced oocytes maturation in carp.
comparative physiology and biochmistry. 01/2008;
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ABSTRACT: The physiological significance of melatonin in the regulation of annual testicular events in a major carp Catla catla was evaluated through studies on the effects of graded dose (25, 50, or 100 microg/100 g body wt.) of melatonin exogenously administered for different durations (1, 15, or 30 days) and manipulation of the endogenous melatonin system by exposing the fish to constant darkness (DD) or constant light (LL) for 30 days. An identical experimental schedule was followed during the preparatory (February-March), pre-spawning (April-May), spawning (July-August), and post-spawning (September-October) phases of the annual cycle. Irrespective of the reproductive status of the carp, LL suppressed while DD increased the mid-day and mid-night values of melatonin compared to respective controls. Influences of exogenous melatonin varied in relation to the dose and duration of treatment and the reproductive status of the carp. However, testicular response to exogenous melatonin (at 100 microg, for 30 days) and DD in each reproductive phase was almost identical. Notably, precocious testicular maturation occurred in both DD and melatonin-injected fish during the preparatory phase and in LL carps during the pre-spawning phase. In contrast, testicular functions in both the melatonin-treated and DD fish were inhibited during the pre-spawning and spawning phases, while the testes did not respond to any treatment during the post-spawning phase. In conclusion, this study provided the first experimental evidence that melatonin plays a significant role in the regulation of annual testicular events in a sub-tropical surface-dwelling carp Catla catla, but the influence of this pineal hormone on the seasonal activity of testis varies in relation to the reproductive status of the concerned fish.
Chronobiology International 02/2007; 24(4):629-50. · 4.03 Impact Factor
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ABSTRACT: Fish (Channa punctatus Bloch) were exposed in vivo for 14 days to non-lethal doses of As2O3 (10% LC50 and 5% LC50). Several endpoints related to histoarchitectural and acetylcholine-acetylcholinesterase (ACh-AChE) profile in the optic tectum were evaluated. Histological examination showed aggregated, disorganized and necrotic cells with irregular outlines in the different layers of optic tectum in the As-treated fish. The histopathological changes were more pronounced on day 7 than on other days and the damage was found to recover on day 14. ACh content and AChE activity demonstrated the usual inverse trend. Arsenic treatment was associated with a dose-dependent increase in AChE activity on day 1, a decrease on day 2 and reactivation on day 7, returning to the basal level on day 14. In vitro inhibition kinetics were set up to determine I50 (35 microM) concentration of As2O3. The ameliorative potential of selenium on arsenic-mediated inhibition of AChE revealed a positive role of Se, especially when Se preceded As2O3 treatment, either in vitro or in vivo.
Comparative Biochemistry and Physiology Part C Toxicology & Pharmacology 10/2006; 144(1):16-24. · 2.62 Impact Factor
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ABSTRACT: Importance of melatonin (N-acetyl-5-methoxytryptamine) in the regulation of oocyte maturation has been studied in a carp Catla catla. Melatonin secretory cells were immunocytochemically localized only in the end vesicle. Diurnal and seasonal studies indicated that the serum levels of melatonin exhibit a minimum diurnal value in the mid-day of all seasons, but the peak value is attained either at mid-night or just before the onset of light. Moreover, highest seasonal value of melatonin was noted in the post-spawning phase. Administration of melatonin at different doses (25, 50, or 100 mug/100 g body weight) for 1, 15, or 30 days resulted in either pro- or anti-gonadal effects depending on the reproductive seasons. In vitro study revealed that incubation of oocytes with melatonin 4h prior to addition of MIH in the medium led to an accelerated rate of oocyte maturation through the formation of a complex of two proteins (MPF), cyclin B and cyclin dependant kinase, Cdc2. Moreover, melatonin pre-incubation considerably increased MIH stimulation of histone H1 phosphorylation as compared to MIH alone. Taken together, gathered information promotes the idea of a physiological role of melatonin in the maturation of oocytes in Catla catla.
Fish Physiology and Biochemistry 04/2005; 31(2-3):201-7. · 1.53 Impact Factor
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ABSTRACT: The present communication is an attempt to demonstrate the influence of melatonin on the action of maturation inducing hormone (MIH) on the maturation of oocytes in carps. The oocytes from gravid female major carp Labeo rohita were isolated and incubated separately in Medium 199 containing (a) only MIH (1 microg/ml), (b) only melatonin (at concentrations of 50, 100 or 500 pg/ml), and (c) both melatonin and MIH, but at different time intervals. In the latter group, melatonin was added to the incubating medium either (i) 4 h before addition of MIH, (ii) 2 h before addition of MIH, (iii) co-administered with MIH (0 h interval) or (iv) 2 h after addition of MIH. In each case, oocytes were further incubated for 4, 8, 12 or 16 h post- administration of MIH, and the effects of treatment on oocyte maturation were evaluated by considering the rate (%) of germinal vesicle breakdown (GVBD). Incubation of oocytes in a medium containing only melatonin did not result in GVBD of any oocyte. Nearly all the oocytes underwent GVBD when incubated with MIH for 16 h. Administration of melatonin along with MIH (at 0 h interval) or 2 h after addition of MIH did not result in any significant change in the rate of GVBD compared to that in a medium containing only MIH. However, it was quite interesting to observe that incubation of oocytes with melatonin especially 4 h prior to addition of MIH in the medium, led to an accelerated rate of GVBD in the oocytes. Experiments with the oocytes of another major carp Cyprinus carpio following an identical schedule depicted similar results except a difference in the optimum melatonin dose. In L. rohita, 50 pg/ml melatonin had maximum acceleratory effect on MIH-induced GVBD of oocytes, while it was 100 pg/ml in C. carpio. Further study revealed that pre-incubation with melatonin accelerates the action of MIH on the formation of a complex of two proteins (MPF), a regulatory component called cyclin B and the catalytic component protein kinase known as cyclin-dependent kinase, Cdk1. Densitometric analysis of the immunoblot data collected from the melatonin pre-treated MIH incubated oocytes showed that cyclin B level continued to increase even after 4 h of incubation, and reached the peak after 12 h. Moreover, determination of H1 kinase activity as an indicator of MPF activity in oocytes revealed that melatonin pre-incubation considerably increased MIH stimulation of histone H1 phosphorylation as compared to MIH alone. Thus, the present study demonstrates for the first time that prior incubation with melatonin accelerates the action of MIH on carp oocyte maturation.
General and Comparative Endocrinology 03/2005; 140(3):145-55. · 3.27 Impact Factor
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ABSTRACT: We studied the localization, sub-cellular distribution and daily rhythms of a 37 kDa melatonin receptor (Mel1aR) in the ovary to assess its temporal relationship with the serum melatonin levels in four different reproductive phases in carp Catla catla. Our immunocytochemical study accompanied by Western blot analysis of Mel1aR in the ovary revealed that the expression of this 37-kDa protein was greater in the membrane fraction than in the cytosol. Ovarian Mel1aR protein peaked at midnight and fell at midday in each reproductive phase. Conversely, serum melatonin levels in the same fish demonstrated a minimum diurnal value at midday in all seasons, but a peak at midnight (during pre-spawning, spawning, and post-spawning phases) or at late dark phase (during preparatory phase). In an annual cycle, band intensity of Mel1aR protein showed a maximum at night in the spawning phase and a minimum in the post-spawning phase, demonstrating an inverse relationship with the levels of serum melatonin. Our data provide first evidence of the presence of Mel1a melatonin receptor in carp ovary and offer interesting perspectives especially for the study of the mechanisms of the control of its rhythmicity and its response to external factors.
Comparative Biochemistry and Physiology - Part A: Molecular & Integrative Physiology.
