Pineal, retinal and harderian gland melatonin in a diurnal species, the richardson's ground squirrel (Spermophilus richardsonii)

Reíter, Russel J.; Richardson, Bruce A.; Hurlbut, Edward C.

doi:10.1016/0304-3940(81)90120-8

Cited by 65 publications

(17 citation statements)

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“…In the eye, melatonin was localized immunohistologically in cell bodies of rods and cones [21][22][23] and the regulation of its synthesis and its physiological significance were elucidated [24]. Shortly after the discovery in the retina, melatonin was also identified in non-neural tissues, such as the Harderian gland (HG) [22,25,26] and the salivary glands of the palate [27]. As the melatonin-synthesizing enzyme hydroxyindole-Omethyltransferase (HIOMT) was also localized in the pineal, retina and the HG [28], it became obvious, that the extrapineal production of melatonin might be more common than was originally anticipated [29].…”

Section: Localizationmentioning

confidence: 99%

Localization, Physiological Significance and Possible Clinical Implication of Gastrointestinal Melatonin

2001

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The gastrointestinal tract (GIT) is a major source of extrapineal melatonin. In some animals, tissue concentrations of melatonin in the GIT surpass blood levels by 10–100 times and the digestive tract contributes significantly to melatonin concentrations in the peripheral blood, particularly during the day. Some melatonin found in the GIT may originate from the pineal gland, as the organs of the digestive system contain binding sites, which in some species exhibit circadian variation. Unlike the production of pineal melatonin, which is under the photoperiodic control, release of GI melatonin seems to be related to periodicity of food intake. Melatonin and melatonin binding sites were localized in all GI tissues of mammalian and avian embryos. Postnatally, melatonin was localized in the GIT of newborn mice and rats. Phylogenetically, melatonin and melatonin binding sites were detected in GIT of numerous mammals, birds and lower vertebrates. Melatonin is probably produced in the serotonin-rich enterochromaffin cells (EC) of the GI mucosa and can be released into the portal vein postprandially. In addition, melatonin can act as an autocrine or a paracrine hormone affecting the function of GI epithelium, lymphatic tissues of the immune system and the smooth muscles of the digestive tube. Finally, melatonin may act as a luminal hormone, synchronizing the sequential digestive processes. Higher peripheral and tissue levels of melatonin were observed not only after food intake but also after a long-term food deprivation. Such melatonin release may have a direct effect on the various GI tissues but may also act indirectly via the CNS; such action might be mediated by sympathetic or parasympathetic nerves. Melatonin can protect GI mucosa from ulceration by its antioxidant action, stimulation of the immune system and by fostering microcirculation and epithelial regeneration. Melatonin may reduce the secretion of pepsin and the hydrochloric acid and influence the activity of the myoelectric complexes of the gut via its action in the CNS. Tissue or blood levels of melatonin may serve as a marker of GI lesions or tumors. Clinically, melatonin has a potential for a prevention or treatment of colorectal cancer, ulcerative colitis, irritable bowel syndrome, children colic and diarrhea.

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Section: Localizationmentioning

confidence: 99%

Localization, Physiological Significance and Possible Clinical Implication of Gastrointestinal Melatonin

2001

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“…We speculated that exposure to sunlight renders humans less sensitive to light (Lewy et al 1980b). In fact, squirrels tested immediately after being caught in the wild require bright light for melatonin suppression (Reiter et al 1981). Subsequent human studies have documented the relationship between history of prior exposure and sensitivity to light (Hebert et al 2002;Smith et al 2004).…”

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Melatonin and Human Chronobiology

Lewy

2007

Cold Spring Harbor Symposia on Quantitative Biology

114

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“…Although exposure to a light irradiance of 350-400 uW/ cm2 for one night is insufficient to prevent the nighttime rise in either pineal NAT or melatonin levels in the Richard son's ground squirrel [4,19], when light is prolonged for I week it totally obliterates the NAT rhythm and greatly re duces the 24-hour cycle of melatonin ( fig. I).…”

Section: Discussionmentioning

confidence: 99%

“…In the Richardson's ground squirrel, it appears that the quantity of melato nin formed may be in part related to the duration of the daily dark period. The Richardson's ground squirrel, Spermophilus richard sonii, is a diurnally active rodent that has been used rather extensively in recent years to investigate the effects of light on the pineal melatonin rhythm [4,18,19]. Pineal melatonin production in this species is of considerable interest inas much as normal artificial room light, which has an irradi ance of roughly 200-300 pW/cm2, is insufficient to prevent the nocturnal rise in pineal melatonin production [4,17], By comparison, pineal melatonin synthesis in nocturnally ac tive rodents including the Syrian hamster (Mesocricetus auratus) and the cotton rat (Sigmodon hispidus) can be sup- Received: December 19, 1983 Accepted after revision: March 23, 1984 pressed by a light irradiance of 0.1 pW/cm2 or less [2,23].…”

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Changes in Serotonin Levels, N-Acetyltransferase Activity, Hydroxyindole-O-Methyltransferase Activity, and Melatonin Levels in the Pineal Gland of the Richardson’s Ground Squirrel in Relation to the Light-Dark Cycle

et al. 1984

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Pineal serotonin and melatonin levels and the activities of hydroxyindole-0-rnethyltransferase (HIOMT) and N-acetyltransferase (NAT) were studied over a 24-hour period in the pineal gland of the diurnally active Richardson’s ground squirrel (Spermophilus richardsonii). Under alternating light-dark conditions (light:dark hours 14:10), pineal serotonin and melatonin levels exhibited a rhythm with high values occurring either during the day (serotonin) or during the night (melatonin). NAT activity was also markedly increased during darkness. HIOMT activity exhibited no 24-hour variation. Exposure of squirrels to constant light for 7 days exaggerated the serotonin rhythm, but obliterated the cycles of NAT and melatonin. Under constant darkness (for 7 days), the rhythms in serotonin, melatonin and NAT persisted, each having a period of about 24 h. In the second study, ground squirrels were exposed to light-dark cycles of either 8:16, 10:14 or 14:10. Under each of these photoperiodic environments, rhythms in pineal NAT and melatonin were apparent. Increasing the daily dark period from 10 to 14 h caused a prolongation of the elevated NAT and melatonin levels. However, a further prolongation of the daily dark period (to 16 h) did not further increase the duration of the rise in NAT and melatonin. The results show that continual light exposure (irradiance of 200 µW/cm²) for 7 days suppresses the pineal rhythms in both NAT activity and melatonin level in the Richardson’s ground squirrel. Conversely, light exposure, rather than depressing the serotonin rhythm, actually exaggerates it. Constant darkness for 7 days has little influence on the 24-hour rhythms of either NAT or melatonin. In the Richardson’s ground squirrel, it appears that the quantity of melatonin formed may be in part related to the duration of the daily dark period.

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Pineal, retinal and harderian gland melatonin in a diurnal species, the richardson's ground squirrel (Spermophilus richardsonii)

Cited by 65 publications

References 16 publications

Localization, Physiological Significance and Possible Clinical Implication of Gastrointestinal Melatonin

Localization, Physiological Significance and Possible Clinical Implication of Gastrointestinal Melatonin

Melatonin and Human Chronobiology

Changes in Serotonin Levels, N-Acetyltransferase Activity, Hydroxyindole-O-Methyltransferase Activity, and Melatonin Levels in the Pineal Gland of the Richardson’s Ground Squirrel in Relation to the Light-Dark Cycle

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