Current state of knowledge on the centrifugal visual system (including the pinealo-to-retinal connection) in mammals and its hypothesized role in circadian rhythms
The ubiquity of circadian rhythms in living organisms has generally been accepted by researchers over the last century. Indeed, morphology and molecular biology of the circadian clock were described during the last fifty years. This main biological clock is located in the suprachiasmatic nucleus of...
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| Language: | English |
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Open Exploration Publishing Inc.
2024-02-01
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| Series: | Exploration of Neuroscience |
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| Online Access: | https://www.explorationpub.com/Journals/en/Article/100636 |
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| author | Viktória Vereczki Katalin Köves Ágnes Csáki |
| author_facet | Viktória Vereczki Katalin Köves Ágnes Csáki |
| author_sort | Viktória Vereczki |
| collection | DOAJ |
| description | The ubiquity of circadian rhythms in living organisms has generally been accepted by researchers over the last century. Indeed, morphology and molecular biology of the circadian clock were described during the last fifty years. This main biological clock is located in the suprachiasmatic nucleus of the hypothalamus. This nucleus is connected with the retina by the retinohypothalamic tract. This way, light regulates the functioning of the biological clock and biological rhythms such as the sleep-wake cycle and other cyclic functions by releasing melatonin from the pineal body (PB) into the general circulation. Melatonin reaches the retina via the bloodstream as humoral feedback. More than a hundred years ago a reverse neuronal connection between the central nervous system and the retina was hypothesized. This so-called centrifugal visual or retinopetal system has been explored in detail in birds, but less information is available in mammals. In this work, the morphology and physiology of mammalian centrifugal visual pathways are reviewed. It is generally accepted that the centrifugal (retinopetal) fibers terminate mainly on the amacrine cells of the retina. Histaminergic fibers terminate on dopaminergic amacrine cells. Serotoninergic synapses were identified on ganglion cells. In addition, serotoninergic fibers were also associated with photoreceptor terminals. Luteinizing hormone releasing hormone fibers have been observed in birds, but not in mammalian retinas. In summary, based on the data available in the literature, it seems that the retinopetal system has a mandatory role in lower vertebrates, but a modulatory role in mammals. There is currently no adequate way to eliminate the centrifugal visual system that would better explain its true function. |
| first_indexed | 2024-03-07T21:26:14Z |
| format | Article |
| id | doaj.art-d1a65a8d658641029bf3175576dd7590 |
| institution | Directory Open Access Journal |
| issn | 2834-5347 |
| language | English |
| last_indexed | 2024-03-07T21:26:14Z |
| publishDate | 2024-02-01 |
| publisher | Open Exploration Publishing Inc. |
| record_format | Article |
| series | Exploration of Neuroscience |
| spelling | doaj.art-d1a65a8d658641029bf3175576dd75902024-02-27T05:13:15ZengOpen Exploration Publishing Inc.Exploration of Neuroscience2834-53472024-02-0131516410.37349/en.2024.00036Current state of knowledge on the centrifugal visual system (including the pinealo-to-retinal connection) in mammals and its hypothesized role in circadian rhythmsViktória Vereczki0Katalin Köves1https://orcid.org/0000-0002-3244-5202Ágnes Csáki2Department of Molecular Genetics and the National Tumour Biology Laboratory, National Institute of Oncology, H-1122 Budapest, HungaryDepartment of Anatomy, Histology and Embryology, Faculty of Medicine, Semmelweis University, H-1094 Budapest, HungaryDepartment of Anatomy, Histology and Embryology, Faculty of Medicine, Semmelweis University, H-1094 Budapest, HungaryThe ubiquity of circadian rhythms in living organisms has generally been accepted by researchers over the last century. Indeed, morphology and molecular biology of the circadian clock were described during the last fifty years. This main biological clock is located in the suprachiasmatic nucleus of the hypothalamus. This nucleus is connected with the retina by the retinohypothalamic tract. This way, light regulates the functioning of the biological clock and biological rhythms such as the sleep-wake cycle and other cyclic functions by releasing melatonin from the pineal body (PB) into the general circulation. Melatonin reaches the retina via the bloodstream as humoral feedback. More than a hundred years ago a reverse neuronal connection between the central nervous system and the retina was hypothesized. This so-called centrifugal visual or retinopetal system has been explored in detail in birds, but less information is available in mammals. In this work, the morphology and physiology of mammalian centrifugal visual pathways are reviewed. It is generally accepted that the centrifugal (retinopetal) fibers terminate mainly on the amacrine cells of the retina. Histaminergic fibers terminate on dopaminergic amacrine cells. Serotoninergic synapses were identified on ganglion cells. In addition, serotoninergic fibers were also associated with photoreceptor terminals. Luteinizing hormone releasing hormone fibers have been observed in birds, but not in mammalian retinas. In summary, based on the data available in the literature, it seems that the retinopetal system has a mandatory role in lower vertebrates, but a modulatory role in mammals. There is currently no adequate way to eliminate the centrifugal visual system that would better explain its true function.https://www.explorationpub.com/Journals/en/Article/100636rathamsterpineal bodyvirus labelingelectron microscopyimmunostainingdouble labeling |
| spellingShingle | Viktória Vereczki Katalin Köves Ágnes Csáki Current state of knowledge on the centrifugal visual system (including the pinealo-to-retinal connection) in mammals and its hypothesized role in circadian rhythms Exploration of Neuroscience rat hamster pineal body virus labeling electron microscopy immunostaining double labeling |
| title | Current state of knowledge on the centrifugal visual system (including the pinealo-to-retinal connection) in mammals and its hypothesized role in circadian rhythms |
| title_full | Current state of knowledge on the centrifugal visual system (including the pinealo-to-retinal connection) in mammals and its hypothesized role in circadian rhythms |
| title_fullStr | Current state of knowledge on the centrifugal visual system (including the pinealo-to-retinal connection) in mammals and its hypothesized role in circadian rhythms |
| title_full_unstemmed | Current state of knowledge on the centrifugal visual system (including the pinealo-to-retinal connection) in mammals and its hypothesized role in circadian rhythms |
| title_short | Current state of knowledge on the centrifugal visual system (including the pinealo-to-retinal connection) in mammals and its hypothesized role in circadian rhythms |
| title_sort | current state of knowledge on the centrifugal visual system including the pinealo to retinal connection in mammals and its hypothesized role in circadian rhythms |
| topic | rat hamster pineal body virus labeling electron microscopy immunostaining double labeling |
| url | https://www.explorationpub.com/Journals/en/Article/100636 |
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