Retinal Ganglion Cells Are Autonomous Circadian Oscillators Synthesizing N-Acetylserotonin during the Day
Autor: | Marcela A Brocco, Beatriz L. Caputto, María I. Keller Sarmiento, A.R. Carpentieri, Maria Ana Contin, Pedro Panzetta, Ruth E. Rosenstein, Eduardo Garbarino-Pico, Mario E. Guido |
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Rok vydání: | 2004 |
Předmět: |
Retinal Ganglion Cells
Serotonin medicine.medical_specialty Time Factors Period (gene) Radioimmunoassay Chick Embryo Biology Arylalkylamine N-Acetyltransferase Biochemistry Retinal ganglion Retina Melatonin chemistry.chemical_compound Oscillometry Internal medicine N-Acetylserotonin Cyclic AMP medicine Animals RNA Messenger Circadian rhythm Molecular Biology In Situ Hybridization Tryptophan Glutamate receptor Brain Retinal Cell Biology Blotting Northern Circadian Rhythm Endocrinology chemistry Arylalkylamine RNA sense organs Chickens medicine.drug |
Zdroj: | Journal of Biological Chemistry. 279:51172-51181 |
ISSN: | 0021-9258 |
Popis: | Retinal ganglion cells send visual and circadian information to the brain regarding the environmental light-dark cycles. We investigated the capability of retinal ganglion cells of synthesizing melatonin, a highly reliable circadian marker that regulates retinal physiology, as well as the capacity of these cells to function as autonomous circadian oscillators. Chick retinal ganglion cells presented higher levels of melatonin assessed by radioimmunoassay during both the subjective day in constant darkness and the light phase of a light-dark cycle. Similar changes were observed in mRNA levels and activity of arylalkylamine N-acetyltransferase, a key enzyme in melatonin biosynthesis, with the highest levels of both parameters during the subjective day. These daily variations were preceded by the elevation of cyclic-AMP content, the second messenger involved in the regulation of melatonin biosynthesis. Moreover, cultures of immunopurified retinal ganglion cells at embryonic day 8 synchronized by medium exchange synthesized a [3H]melatonin-like indole from [3H]tryptophan. This [3H]indole was rapidly released to the culture medium and exhibited a daily variation, with levels peaking 8 h after synchronization, which declined a few hours later. Cultures of embryonic retinal ganglion cells also showed self-sustained daily rhythms in arylalkylamine N-acetyltransferase mRNA expression during at least three cycles with a period near 24 h. These rhythms were also observed after the application of glutamate. The results demonstrate that chick retinal ganglion cells may function as autonomous circadian oscillators synthesizing a melatonin-like indole during the day. |
Databáze: | OpenAIRE |
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