Light affects neonatal rat pineal gland N-acetyltransferase activity by an extra-retinal mechanism

Torres, Germán; Lytle, Loy D.

doi:10.1007/bf01245023

Cited by 9 publications

(10 citation statements)

References 24 publications

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“…Certain other rod and cone-specific phototransduction components, however, are absent from the pineal. Our findings support other evidence indicating that mammalian pineal glands are physiologically photosensitive in early life (Zweig et al, 1966;Machado et al, 1969a,b;Wetterberg et al, 1970;Torres and Lytle, 1990) and fit with known features of retina and pineal development. The eyes of a rat do not open until the third week of life, so that at earlier stages the pineal gland, which is located quite superficially underneath the very thin neonatal skull, receives more incident light than the retina (Torres and Lytle, 1990).…”

Section: Discussionsupporting

confidence: 92%

“…Findings that neonatal pinealocytes show photoreceptor-like differentiation in vivo (Zimmerman and Tso, 1975) and in vitro (Araki, 1992) favor direct detection of light by neonatal rat pineal. Regulation of the melatonin-forming enzyme serotonin N-acetyltransferase (NAT) has been demonstrated in blinded neonatal rats in some studies (Torres and Lytle, 1990), but not in others (Deguchi, 1982b;Reppert et al, 1984). It has not proved feasible to demonstrate light-induced electrophysiological changes in dissociated rat pinealocytes nor modulation of melatonin production in neonatal pineal cultures (Brammer and Binkley, 1981).…”

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confidence: 99%

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Developmental Expression Pattern of Phototransduction Components in Mammalian Pineal Implies a Light-Sensing Function

1997

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Whereas the pineal organs of lower vertebrates have been shown to be photosensitive, photic regulation of pineal function in adult mammals is thought be mediated entirely by retinal photoreceptors. Extraretinal regulation of pineal function has been reported in neonatal rodents, although both the site and molecular basis of extraretinal photoreception have remained obscure. In this study we examine the developmental expression pattern of all of the principal components of retinal phototransduction in rat pineal via cRNA in situ hybridization. All of the components needed to reconstitute a functional phototransduction pathway are expressed in the majority of neonatal pinealocytes, although the expression levels of many of these genes decline dramatically during development. These findings strongly support the theory that the neonatal rat pineal itself is photosensitive. In addition, we observe in neonatal pinealocytes the expression of both rod-specific and cone-specific phototransduction components, implying the existence of functionally different subtypes of pinealocytes that express varying combinations of phototransduction enzymes.

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Section: Discussionsupporting

confidence: 92%

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confidence: 99%

Developmental Expression Pattern of Phototransduction Components in Mammalian Pineal Implies a Light-Sensing Function

1997

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“…This form of extraocular photoreception disappears after about 6 days of age (Torres and Lytle 1990). There is evidence to suggest that the neonatal rat pineal gland contains photoreceptors particularly sensitive to blue light (Blackshaw and Snyder 1997).…”

Section: Extraocular Light and Reentrainment 811mentioning

confidence: 96%

Failure of Extraocular Light to Facilitate Circadian Rhythm Reentrainment in Humans

Eastman

Martin

Hébert

2000

Chronobiology International

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Although extraocular light can entrain the circadian rhythms of invertebrates and nonmammalian vertebrates, almost all studies show that the mammalian circadian system can only be affected by light to the eyes. The exception is a recent study by Campbell and Murphy that reported phase shifts in humans to bright light applied with fiber-optic pads behind the knees (popliteal region). We tested whether this extraocular light stimulus could accelerate the entrainment of circadian rhythms to a shift of the sleep schedule, as occurs in shift work or jet lag. In experiment 1, the sleep/dark episodes were delayed 8h from baseline for 2 days, and 3h light exposures were timed to occur before the temperature minimum to help delay circadian rhythms. There were three groups: (1) bright (about 13,000 lux) extraocular light from fiber-optic pads, (2) control (dim light, 10-20 lux), and (3) medium-intensity (about 1000 lux) ocular light from light boxes. In experiment 2, the sleep/dark episodes were inverted, and extraocular light was applied either before the temperature minimum to help delay circadian rhythms or after the temperature minimum to help advance rhythms. Circadian phase markers were the salivary dim light melatonin onset (DLMO) and the rectal temperature minimum. There was no evidence that the popliteal extraocular light had a phase-shifting effect in either experiment. Possible reasons for phase shifts in the Campbell and Murphy study and not the current study include the many differences between the protocols. In the current study, there was substantial sleep deprivation before the extraocular light was applied. There was a large shift in the sleep/dark schedule, rather than allowing subjects to sleep each day from midnight to noon, as in the Campbell and Murphy study. Also, when extraocular light was applied in the current protocol, subjects did not experience a change from sleeping to awake, a change in posture (from lying in bed to sitting in a chair), or a change in ocular light (from dark to dim light). Further research is necessary to determine the conditions under which extraocular light might produce phase shifts in human circadian rhythms.

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“…Torres and Lytle (5,6) showed that exposing blinded neonatal rats to light during the subjective night significantly reduced the activity of the melatonin-forming enzyme arylalkylamine N-acetyltransferase (AA-NAT). Sympathectomy of neonatal rat pineal does not interfere with light entrainment of pineal melatonin in the first weeks of life, whereas sympathectomy at later postnatal ages abolishes light entrainment (7,8).…”

mentioning

confidence: 99%

Induction of photosensitivity in neonatal rat pineal gland

Tosini¹,

Doyle²,

Geusz³

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

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Pineal glands removed from neonatal rats at 5, 7, and 9 days of age and explanted into short-term culture, synthesized melatonin when stimulated with norepinephrine (NE); their melatonin synthesis could not be suppressed with bright white light. Dispersed pineal cell cultures or pineal explants prepared from 1-day-old neonates and held in culture for 7 or 9 days also synthesized melatonin when stimulated with NE, but in these cases melatonin synthesis was significantly suppressed by light, demonstrating that the pineals had become photosensitive while in culture. The development of photosensitivity in culture could be partially or completely abolished by the continuous presence of 1 or 10 m of NE in the culture medium. The pineals of all nonmammalian vertebrates are photoreceptive, whereas those of mammals do not normally respond to light. We hypothesize that a mechanism to suppress pineal photosensitivity by using NE released from sympathetic nerve endings evolved early in the history of mammals.

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Light affects neonatal rat pineal gland N-acetyltransferase activity by an extra-retinal mechanism

Cited by 9 publications

References 24 publications

Developmental Expression Pattern of Phototransduction Components in Mammalian Pineal Implies a Light-Sensing Function

Developmental Expression Pattern of Phototransduction Components in Mammalian Pineal Implies a Light-Sensing Function

Failure of Extraocular Light to Facilitate Circadian Rhythm Reentrainment in Humans

Induction of photosensitivity in neonatal rat pineal gland

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