Photoperiod effects on hypothalamic serotonergic activity in the goldfish, Carassius auratus (original) (raw)
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Comparative biochemistry and physiology. C: Comparative pharmacology, 1979
The effects of photoperiod acclimation, pinealectomy, and sampling time on monoamme oxidase (MAO) activity in the basal medial lobe of the goldfish (Carassius auratus) hypothalamus were examined. 2. A significant daily variation in MAO activity was observed in fish exposed to a long, but not the short photoperiod. 3. MAO activity was depressed in fish exposed to a short, as compared to a long photoperiod. 4. Pinealectomy elevated hypothalamic MAO activity in fish exposed to a short photoperiod, but had no obvious effect on enzyme activity in fish exposed to a long photoperiod. 5. The effects of pinealectomy on hypothalamic MAO activity seem to vary with season.
Fish Physiology and Biochemistry, 2000
Reproduction in fish is cyclical and timed to guarantee the survival of the offspring. Seasonal variations in reproductive hormones of fish have been deeply investigated in fish over the last years. However, there are few studies regarding the daily changes in reproductive hormone profiles in teleosts. The aim of the present research was to investigate the effects of photoperiod manipulation on melatonin and reproductive hormones (pituitary sbGnRH, pituitary LH and plasma LH, testosterone [T], and 11-ketotestosterone [11KT]) daily rhythms in male sea bass, kept in net cages under farming conditions in winter (9L:15D). Fish were distributed in two groups, one under constant long photoperiod (18L:6D) and the other under natural photoperiod. The photoperiod strongly influenced the daily melatonin profile, so that the duration of the nocturnal melatonin rise was longer in the control group than in the group exposed to the artificial photoperiod (18L:6D). A daily rhythm was observed in the pituitary sbGnRH profile in both groups, showing the lowest levels during the dark period. A daily rhythm of pituitary LH was detected in the control group, which was suppressed in the group under long photoperiod. Daily variations in plasma LH were observed, the highest levels being found in the dark phase in both groups, although this profile was significantly altered by artificial light, maintaining a fixed relationship between the first nocturnal rise of melatonin and the nocturnal peaks of plasma LH in both groups. Plasma T levels showed significant fluctuations in their daily cycle following a sinusoidal pattern with an acrophase around sunrise in both groups, without any influence of light regime. No significant daily variations in plasma levels of 11-KT were observed in none of the groups. Our results provide the first evidence of the presence of daily variations in pituitary sbGnRH content, pituitary and plasma LH, and plasma T in sea bass. Artificial lights suppressed the circulating melatonin and significantly affected the daily rhythm of LH storage and release.
Annual variation in photoperiod is the most regular phenomenon that has strong predictive value in the temporal organization of seasonal activities in biological world, especially reproduction. Carefully controlled studies demonstrated importance of photoperiods in the regulation of annual reproductive events in diverse groups of animals including fish. Apart from academic interests, study in fish has gained momentum because of its tremendous economic importance as food. Thus, for obvious reasons, efforts are continued to develop technologies for increasing fecundity and growth of fish in culture. As a result, photoperiodic manipulation has emerged as an effective tool of reproductive management in culture fisheries, and understanding the physiology of photoperiodic regulation of fish reproduction became the priority topic of research in different countries. The present paper reviews and summarizes the information gathered in recent years on the importance of photoperiod and the mechanism of photoperiodic signal transduction in the photo-neuroendocrine system in fish emphasizing the role of pineal organ, which is considered as an intermediary between the environment and the endocrine system in vertebrates.
Melatonin reduces locomotor activity and circulating cortisol in goldfish
Hormones and Behavior, 2010
The present study focused on the effects of a subchronic melatonin treatment on locomotor activity and cortisol plasma levels in goldfish. We compared two different administration routes: peripheral (10 μg/g body weight) versus central (1 μg/μl) injections of melatonin for 7 or 4 days, respectively. Daily locomotor activity, including both diurnal and nocturnal activities, food anticipatory activity and circulating cortisol at 11:00 (under 24 h of food deprivation and 17 h postinjection) were significantly reduced after repeated intraperitoneal injections with melatonin for 7 days, but not after intracerebroventricular treatment. Taking in mind the anoretic effect of melatonin in this species, we investigated if such feeding reduction is directly responsible for the reduction in motor activity induced by melatonin treatment. Food restriction (50%) for 10 days did not significantly modify either daily locomotor activity or plasma cortisol levels in goldfish, indicating that the peripheral action of melatonin diminishing locomotor activity in goldfish is not a direct consequence of its anoretic action. In summary, our results indicate that, as previously described in other vertebrate species, melatonin can regulate locomotor activity and cortisol levels in goldfish, suggesting a sedative effect of this hormone in this teleost.
2017
Annual variation of photoperiod is the most regular phenomenon that has strong predictive value in the temporal organization of seasonal activities in biological world, especially reproduction. The pineal organ, has the most important role in melatonin release under the different light condition. Melatonin is a much conserved feature in vertebrates that plays a central role in the entrainment of daily and annual physiological rhythms. The present study carried out in order to underestand different light intensity and photoperiod effects on melatonin release in whitespotted rabbitfish (siganus sutor) brood stock. For this purpose, 9 treatments, under artificial lighting conditions with 3 levels of photoperiod and light intensity include (16L/8D), (12L/12D), (6L/16D) and 1000, 2000, 3000 Lux, with a control treatment (natural light) on a period of 60 days studied. At the end of period analyzing the blood showed that the rate of melatonin in all of the male and female treatments in tre...
Zoological science, 2003
Daily variations in plasma melatonin levels in the rainbow trout Oncorhynchus mykiss were studied under various light and temperature conditions. Plasma melatonin levels were higher at mid-dark than those at mid-light under light-dark (LD) cycles. An acute exposure to darkness (2 hr) during the light phase significantly elevated the plasma melatonin to the level that is comparable with those at mid-dark, while an acute exposure to a light pulse (2 hr) during the dark phase significantly suppressed melatonin to the level that is comparable with those at mid-light. Plasma melatonin kept constantly high and low levels under constant darkness and constant light, respectively. No circadian rhythm was seen under both conditions. When the fish were subjected to simulative seasonal conditions (simulative (S)-spring: under LD 13.1:10.9 at 13 degrees C; S-summer: under LD 14.3:9.7 at 16.5 degrees C; S-autumn: under LD 11.3:12.7 at 13 degrees C; S-winter: under LD 10.1:13.9 at 9 degrees C), me...
Current knowledge on the melatonin system in teleost fish
2010
Melatonin is a much conserved feature in vertebrates that plays a central role in the entrainment of daily and annual physiological rhythms. Investigations aiming at understanding how melatonin mediates the effects of photoperiod on crucial functions and behaviors have been very active in the last decades, particularly in mammals. In fish a clear-cut picture is still missing.
Chronobiology International, 1988
In Channa punctatus maintained under ambient photothermal conditions (10.5L:13.5D; 13 + 2C) in the postspawning season, hypothalamic dopamine (DA) and norepinephrine (NE) content varied diurnally, but serotonin (5-HT) and monoamine oxidase (MAO) did not. Exposure of the fish to high temperature (25 + 2°C), with or without altering the photopheriod, increased the NE and DA content, and NE turnover but decreased DA turnover. Increasing the photoperiod (16L:8D) alone had no significant effect on catecholaminergic (CA) content or activity. When the fish were exposed to long photoperiod, with or without altering the temperature, a day-night variation in 5-HT content and activity was induced in the postspawning season. An increase in temperature alone had no significant effect on 5-HT content or activity. Hypothalamic MAO activity was elevated in fish exposed to high temperature alone, or in combination with long photoperiod, but was not affected significantly by long photoperiod treatment. These results indicate that CA activity is influenced largely by ambient high temperature, whereas serotonergic activity is controlled primarily by photoperiod, with high temperature having an additive effect. MAO activity seems to be influenced by both temperature and photoperiod in this species.