Regulation of serotonin N-acetyltransferase activity in the chick pineal gland by UV-A and white light: role of MK-801- and SCH 23390-sensitive retinal signals.
Journal Title: Pharmacological Reports - Year 2007, Vol 59, Issue 4
Abstract
The rhythmic melatonin synthesis in the pineal gland is one of the most extensively studied circadian rhythms in vertebrates. Light is the dominant environmental factor controlling this process. Light at night acutely suppresses pineal melatonin content and activity of serotonin N-acetyltransferase (AANAT; the key and penultimate enzyme in the hormone biosynthetic pathway). In addition, pulses of light appropriately timed reset the circadian oscillator generating the melatonin rhythm. Although the avian pineal gland is a directly photosensitive organ, it has recently been demonstrated that light perceived by the eyes only regulates its activity. The present study shows that ocular exposure of chicks to UV-A radiation or white light during the second half of the subjective night markedly decreased AANAT activity in the pineal gland, and produced a significant phase advance of the circadian rhythm of the enzyme activity. Both the suppressive and phase-shifting effects of UV-A light were antagonized by intraocular pretreatment of birds with MK 801 (a selective blocker of NMDA glutamate receptors), but were not modified by SCH 23390 (a selective antagonist of D1-dopamine receptors). On the other hand, the suppressive and phase-shifting effects of retinally perceived white light were antagonized by intraocular injection of SCH 23390, and not affected by MK 801. Our results demonstrate that retinal illumination with UV-A radiation and white light provide powerful signals that shift phase of the circadian oscillator generating melatonin rhythm in the chick pineal gland. It is suggested that control of pineal melatonin synthesis by retinally perceived UV-A and white light might involve input from different photoreceptors.
Authors and Affiliations
Jolanta Zawilska, Anna Lorenc, Małgorzata Berezińska
Keywords
Related Articles
- EP ID EP123695
- DOI -
- Views 89
- Downloads 0
Age-related macular degeneration (AMD): pathogenesis and therapy.
Age-related macular degeneration (AMD) is a disease leading to severe visual loss and legal blindness in the elderly population. Its pathogenesis, likely multifactorial, involving a complex interaction of metabolic, func...
Dose-response relationship analysis of vigabatrin doses and their antinociceptive effects in the hot-plate test in mice.
This study was aimed at determining the analgesic effects of vigabatrin (VGB, a newer antiepileptic drug) in the acute thermal pain model (hot-plate test) in mice. Linear regression analysis was used to evaluate a dose-r...
Trimetazidine increases [3H]glucose uptake in rat brain.
Trimetazidine, a clinically effective antianginal agent with no negative inotropic or vascular properties, acts by optimizing cardiac energy metabolism through inhibition of free fatty acid oxidation, shifting substrate...
Evaluation of terfenadine and ketoconazole-induced QT prolongation in conscious telemetered guinea pigs.
Terfenadine and ketoconazole are the most widely used positive reference agents in non-clinical cardiac repolarization safety studies. The aim of the present study was to evaluate the effects of terfenadine, ketoconazole...
Therapeutic tricyclic antidepressant drug monitoring in younger and older depressive patients.
The present study shows the evaluation of clinical state and serum level of tricyclic antidepressants in thirty-eight depressive younger and elderly patients during 8-week observation. We observed no statistically signif...