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Li H, Jiang T, An S, Xu M, Gou L, Ren B, Shi X, Wang X, Yan J, Yuan J, Xu X, Wu QF, Luo Q, Gong H, Bian WJ, Li A, Yu X. Single-neuron projectomes of mouse paraventricular hypothalamic nucleus oxytocin neurons reveal mutually exclusive projection patterns. Neuron 2024; 112:1081-1099.e7. [PMID: 38290516 DOI: 10.1016/j.neuron.2023.12.022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Revised: 11/07/2023] [Accepted: 12/29/2023] [Indexed: 02/01/2024]
Abstract
Oxytocin (OXT) plays important roles in autonomic control and behavioral modulation. However, it is unknown how the projection patterns of OXT neurons align with underlying physiological functions. Here, we present the reconstructed single-neuron, whole-brain projectomes of 264 OXT neurons of the mouse paraventricular hypothalamic nucleus (PVH) at submicron resolution. These neurons hierarchically clustered into two groups, with distinct morphological and transcriptional characteristics and mutually exclusive projection patterns. Cluster 1 (177 neurons) axons terminated exclusively in the median eminence (ME) and have few collaterals terminating within hypothalamic regions. By contrast, cluster 2 (87 neurons) sent wide-spread axons to multiple brain regions, but excluding ME. Dendritic arbors of OXT neurons also extended outside of the PVH, suggesting capability to sense signals and modulate target regions. These single-neuron resolution observations reveal distinct OXT subpopulations, provide comprehensive analysis of their morphology, and lay the structural foundation for better understanding the functional heterogeneity of OXT neurons.
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Affiliation(s)
- Humingzhu Li
- Institute of Neuroscience and State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China; University of Chinese Academy of Sciences, Beijing 100049, China; School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China; School of Life Sciences, Peking-Tsinghua Center for Life Sciences, and Peking University McGovern Institute, Peking University, Beijing 100871, China
| | - Tao Jiang
- HUST-Suzhou Institute for Brainsmatics, JITRI, Suzhou 215123, China
| | - Sile An
- Britton Chance Center for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics, MoE Key Laboratory for Biomedical Photonics, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Mingrui Xu
- University of Chinese Academy of Sciences, Beijing 100049, China; State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | - Lingfeng Gou
- Institute of Neuroscience and State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China
| | - Biyu Ren
- Institute of Neuroscience and State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China
| | - Xiaoxue Shi
- Institute of Neuroscience and State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China
| | - Xiaofei Wang
- Institute of Neuroscience and State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China
| | - Jun Yan
- Institute of Neuroscience and State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jing Yuan
- HUST-Suzhou Institute for Brainsmatics, JITRI, Suzhou 215123, China; Britton Chance Center for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics, MoE Key Laboratory for Biomedical Photonics, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Xiaohong Xu
- Institute of Neuroscience and State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Qing-Feng Wu
- University of Chinese Academy of Sciences, Beijing 100049, China; State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | - Qingming Luo
- HUST-Suzhou Institute for Brainsmatics, JITRI, Suzhou 215123, China; Britton Chance Center for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics, MoE Key Laboratory for Biomedical Photonics, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Hui Gong
- HUST-Suzhou Institute for Brainsmatics, JITRI, Suzhou 215123, China; Britton Chance Center for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics, MoE Key Laboratory for Biomedical Photonics, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Wen-Jie Bian
- Institute of Neuroscience and State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China; Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou 310024, China; School of Life Sciences, Westlake University, Hangzhou 310024, China.
| | - Anan Li
- HUST-Suzhou Institute for Brainsmatics, JITRI, Suzhou 215123, China; Britton Chance Center for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics, MoE Key Laboratory for Biomedical Photonics, Huazhong University of Science and Technology, Wuhan 430074, China.
| | - Xiang Yu
- Institute of Neuroscience and State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China; University of Chinese Academy of Sciences, Beijing 100049, China; School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China; School of Life Sciences, Peking-Tsinghua Center for Life Sciences, and Peking University McGovern Institute, Peking University, Beijing 100871, China; Chinese Institute for Brain Research, Beijing 102206, China.
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Benedito-Silva AA, Evans S, Viana Mendes J, Castro J, Gonçalves BDSB, Ruiz FS, Beijamini F, Evangelista FS, Vallada H, Krieger JE, von Schantz M, Pereira AC, Pedrazzoli M. Association between light exposure and metabolic syndrome in a rural Brazilian town. PLoS One 2020; 15:e0238772. [PMID: 32946454 PMCID: PMC7500684 DOI: 10.1371/journal.pone.0238772] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Accepted: 08/24/2020] [Indexed: 01/10/2023] Open
Abstract
Context Metabolic syndrome (MetS) is a complex condition comprising a ‘clustering’ of components representing cardiometabolic risk factors for heart disease and diabetes; its prevalence rate is high and consequences serious. Evidence suggests that light exposure patterns and misalignment of circadian rhythms might contribute to MetS etiology by impacting energy metabolism and glucose regulation. Objective We hypothesised that individuals with MetS would show disrupted circadian and sleep parameters alongside differences in light exposure profiles. We investigated this using data from a cohort study in Brazil. Methods Data from 103 individuals from the Baependi Heart Cohort Study aged between 50 and 70 were analysed. Motor activity and light exposure were measured using wrist-worn actigraphy devices. Cardiometabolic data were used to calculate the number of MetS components present in each participant, and participants grouped as MetS/non-MetS according to standard guidelines. Between-group comparisons were made for the actigraphy measures; additionally, correlation analyses were conducted. Results Motor activity and circadian profiles showed no differences between groups. However, the MetS group presented lower light exposure during the day and higher light exposure at night. Correlation analyses, including all participants, showed that greater daytime light exposure and greater light exposure difference between day and night were associated with reduced MetS risk (a lower number of MetS components). Also, the light exposure difference between day and night correlated with body mass index across all participants. Conclusions The observed results suggest a direct association between light exposure and MetS which appears to not be attributable to disruptions in circadian activity rhythm nor to sleep parameters. This link between light exposure patterns and MetS risk could inform possible prevention strategies.
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Affiliation(s)
| | - Simon Evans
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, United Kingdom
| | - Juliana Viana Mendes
- School of Arts, Science and Humanities, University of São Paulo, São Paulo, Brazil
| | - Juliana Castro
- School of Arts, Science and Humanities, University of São Paulo, São Paulo, Brazil
| | | | - Francieli S. Ruiz
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, United Kingdom
- Institute of Psychiatry, University of São Paulo Medical School, São Paulo, Brazil
| | - Felipe Beijamini
- Institute of Psychiatry, University of São Paulo Medical School, São Paulo, Brazil
- Federal University of Fronteira Sul (UFFS), Realeza, Brazil
| | | | - Homero Vallada
- Institute of Psychiatry, University of São Paulo Medical School, São Paulo, Brazil
| | | | - Malcolm von Schantz
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, United Kingdom
| | - Alexandre C. Pereira
- Laboratory of Genetics and Molecular Cardiology, Heart Institute (InCor), University of São Paulo Medical School, São Paulo, Brazil
| | - Mario Pedrazzoli
- School of Arts, Science and Humanities, University of São Paulo, São Paulo, Brazil
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Cipolla-Neto J, Amaral FGD. Melatonin as a Hormone: New Physiological and Clinical Insights. Endocr Rev 2018; 39:990-1028. [PMID: 30215696 DOI: 10.1210/er.2018-00084] [Citation(s) in RCA: 298] [Impact Index Per Article: 49.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Accepted: 06/21/2018] [Indexed: 02/07/2023]
Abstract
Melatonin is a ubiquitous molecule present in almost every live being from bacteria to humans. In vertebrates, besides being produced in peripheral tissues and acting as an autocrine and paracrine signal, melatonin is centrally synthetized by a neuroendocrine organ, the pineal gland. Independently of the considered species, pineal hormone melatonin is always produced during the night and its production and secretory episode duration are directly dependent on the length of the night. As its production is tightly linked to the light/dark cycle, melatonin main hormonal systemic integrative action is to coordinate behavioral and physiological adaptations to the environmental geophysical day and season. The circadian signal is dependent on its daily production regularity, on the contrast between day and night concentrations, and on specially developed ways of action. During its daily secretory episode, melatonin coordinates the night adaptive physiology through immediate effects and primes the day adaptive responses through prospective effects that will only appear at daytime, when melatonin is absent. Similarly, the annual history of the daily melatonin secretory episode duration primes the central nervous/endocrine system to the seasons to come. Remarkably, maternal melatonin programs the fetuses' behavior and physiology to cope with the environmental light/dark cycle and season after birth. These unique ways of action turn melatonin into a biological time-domain-acting molecule. The present review focuses on the above considerations, proposes a putative classification of clinical melatonin dysfunctions, and discusses general guidelines to the therapeutic use of melatonin.
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Affiliation(s)
- José Cipolla-Neto
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
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Garcia RAP, Afeche SC, Scialfa JH, do Amaral FG, dos Santos SHJ, Lima FB, Young ME, Cipolla-Neto J. Insulin modulates norepinephrine-mediated melatonin synthesis in cultured rat pineal gland. Life Sci 2008; 82:108-14. [DOI: 10.1016/j.lfs.2007.10.016] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2007] [Revised: 09/17/2007] [Accepted: 10/22/2007] [Indexed: 10/22/2022]
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5
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Afeche SC, Barbosa R, Scialfa JH, Terra IM, Cassola AC, Cipolla-Neto J. Effects of the blockade of high voltage-activated calcium channels on in vitro pineal melatonin synthesis. Cell Biochem Funct 2007; 24:499-505. [PMID: 16143961 DOI: 10.1002/cbf.1270] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The presence of high voltage-activated calcium channels in the rat pineal gland is well known. However, their role in pineal metabolism is not completely understood and is even controversial. Better to understand this matter, we investigated the effects of L-, N- or P/Q-type calcium channel blockers (nifedipine, omega-conotoxin GVIA, omega-agatoxin IVA, respectively) on melatonin content and arylalkylamine-N-acetyltransferase activity of denervated rat pineal glands kept for 48 h in culture and stimulated with norepinephrine. Melatonin was measured by high performance liquid chromatography with electrochemical detection and arylalkylamine-N-acetyltransferase activity was quantified by radiometric assay. Pre-incubation with any of these high voltage-activated calcium channel blockers reduced the melatonin production induced by norepinephrine although arylalkylamine-N-acetyltransferase activity was reduced only by the N-type calcium channel antagonist, omega-conotoxin GVIA. The results indicate that calcium influx through L-, N- or P/Q-type of high voltage-activated calcium channels is necessary for the full expression of the metabolic process leading to melatonin synthesis in the rat pineal glands. However, the mechanisms involved in this process are different for the L- or P/Q- and N-type calcium channels.
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Affiliation(s)
- Solange C Afeche
- Laboratory of Pharmacology, Butantan Institute, Av. Vital Brazil, 1500 São Paulo, SP 05503-900, Brazil.
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Reaux A, Gallatz K, Palkovits M, Llorens-Cortes C. Distribution of apelin-synthesizing neurons in the adult rat brain. Neuroscience 2002; 113:653-62. [PMID: 12150785 DOI: 10.1016/s0306-4522(02)00192-6] [Citation(s) in RCA: 155] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The peptide apelin originating from a larger precursor preproapelin molecule has been recently isolated and identified as the endogenous ligand of the human orphan G protein-coupled receptor, APJ (putative receptor protein related to the angiotensin receptor AT(1)). We have shown recently that apelin and apelin receptor mRNA are expressed in brain and that the centrally injected apelin fragment K17F (Lys(1)-Phe-Arg-Arg-Gln-Arg-Pro-Arg-Leu-Ser-His-Lys-Gly-Pro-Met-Pro-Phe(17)) decreased vasopressin release and altered drinking behavior. Using a specific polyclonal antiserum against K17F for immunohistochemistry, the aim of the present study was to establish the precise topographical distribution of apelin immunoreactivity in colchicine-treated adult rat brain. Immunoreactivity was essentially detected in neuronal cell bodies and fibers throughout the entire neuroaxis in different densities. Cells bodies have been visualized in the preoptic region, the hypothalamic supraoptic and paraventricular nuclei and in the highest density, in the arcuate nucleus. Apelin immunoreactive cell bodies were also seen in the pons and the medulla oblongata. Apelin nerve fibers appear more widely distributed than neuronal apelin cell bodies. The hypothalamus represented, by far, the major site of apelin-positive nerve fibers which were found in the suprachiasmatic, periventricular, dorsomedial, ventromedial nuclei and in the retrochiasmatic area, with the highest density in the internal layer of the median eminence. Fibers were also found innervating other circumventricular organs such as the vascular organ of the lamina terminalis, the subfornical and the subcommissural organs and the area postrema. Apelin was also detected in the septum and the amygdala and in high density in the paraventricular thalamic nucleus, the periaqueductal central gray matter and dorsal raphe nucleus, the parabrachial and Barrington nuclei in the pons and in the nucleus of the solitary tract, lateral reticular, prepositus hypoglossal and spinal trigeminal nuclei. The topographical distribution of apelinergic neurons in the brain suggests multiple roles for apelin especially in the central control of ingestive behaviors, pituitary hormone release and circadian rhythms.
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Affiliation(s)
- A Reaux
- Institut National de la Santé et de la Recherche Médicale, Unité 36, Collège de France, Chaire de Médecine Expérimentale, 11 Place Marcelin Berthelot, 75005, Paris, France
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7
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Sulli A, Maestroni GJM, Villaggio B, Hertens E, Craviotto C, Pizzorni C, Briata M, Seriolo B, Cutolo M. Melatonin serum levels in rheumatoid arthritis. Ann N Y Acad Sci 2002; 966:276-83. [PMID: 12114284 DOI: 10.1111/j.1749-6632.2002.tb04227.x] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The pineal hormone melatonin (MLT) exerts a variety of effects on the immune system. MLT activates immune cells and enhances inflammatory cytokine and nitric oxide production. Cytokines are strongly involved in the synovial immune and inflammatory response in rheumatoid arthritis (RA) and reach the peak of concentration in the early morning, when MLT serum level is higher. Nocturnal MLT serum levels were evaluated in 10 RA patients and in 6 healthy controls. Blood samples were obtained at 8 and 12 p.m., as well as at 2, 4, 6, and 8 a.m. MLT serum levels at 8 p.m. and 8 a.m. were found to be higher in RA patients than in controls (p < 0.05). In both RA patients and healthy subjects, MLT progressively increased from 8 p.m. to the first hours of the morning, when the peak level was reached (p < 0.02). However, MLT serum level reached the peak at least two hours before in RA patients than in controls (p < 0.05). Subsequently, in RA patients, MLT concentration showed a plateau level lasting two to three hours, an effect not observed in healthy controls. After 2 a.m., MLT levels decreased similarly in both RA patients and healthy subjects. Several clinical symptoms of RA, such as morning gelling, stiffness, and swelling, which are more evident in the early morning, might be related to the neuroimmunomodulatory effects exerted by MLT on synovitis and might be explained by the imbalance between cortisol serum levels (lower in RA patients) and MLT serum levels (higher in RA patients).
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Affiliation(s)
- A Sulli
- Laboratory and Division of Rheumatology, Department of Internal Medicine and Medical Specialities, University of Genova, Genova, Italy.
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Mota SR, Canteras NS, Bartol I, Skorupa AL, Scialfa JH, Terra IM, Afeche SC, Cipolla-Neto J. Lesions of the dorsomedial hypothalamic nucleus do not influence the daily profile of pineal metabolism in rats. Neuroendocrinology 2001; 73:123-8. [PMID: 11244299 DOI: 10.1159/000054628] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The present study attempted to characterize the effects of electrolytic lesions of the hypothalamic dorsomedial nucleus on the daily profile of pineal metabolism as well as on the inhibition of pineal melatonin synthesis induced by acute light exposure during the night. Adult male Wistar rats (n = 107, 12:12 h light-dark cycle) were left intact (n = 47) or lesioned (n = 60). Lesioned rats and their respective controls were killed at six time points distributed throughout the light-dark cycle. At ZT (zeitgeber time) 18 the animals were killed either in the dark or after 15 min of light stimulation. Pineal glands were assayed using high-performance liquid chromatography with electrochemical detection (HPLC-ED). There was no difference in the amounts of pineal indoles between lesioned and control rats under any of the experimental situations tested. These results suggest that in rats, the hypothalamic dorsomedial nucleus does not participate in either the neural control of daily pineal metabolism or the nocturnal light-induced inhibition of the pineal metabolism.
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Affiliation(s)
- S R Mota
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
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9
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Tillet Y, Batailler M, Thiéry JC, Thibault J. Neuronal projections to the lateral retrochiasmatic area of sheep with special reference to catecholaminergic afferents: immunohistochemical and retrograde tract-tracing studies. J Chem Neuroanat 2000; 19:47-67. [PMID: 10882837 DOI: 10.1016/s0891-0618(00)00052-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The retrochiasmatic area contains the A15 catecholaminergic group and numerous monoaminergic afferents whose discrete cell origins are unknown in sheep. Using tract-tracing methods with a specific retrograde fluorescent tracer, fluorogold, we examined the cells of origin of afferents to the retrochiasmatic area in sheep. The retrogradely labeled cells were seen by observation of the tracer by direct fluorescence or by immunohistochemistry with specific antibodies raised in rabbits or horses. Among the retrogradely labeled neurons, double immunohistochemistry for tyrosine hydroxylase, dopamine-beta-hydroxylase, and serotonin were used to characterize catecholamine and serotonin FG labeled neurons. The retrochiasmatic area, which included the A15 dopaminergic group and the accessory supraoptic nucleus (SON), received major inputs from the lateral septum (LS), the bed nucleus of the stria terminalis (BNST), the thalamic paraventricular nucleus, hypothalamic paraventricular and supraoptic nuclei, the perimamillary area, the amygdala, the ventral part of the hippocampus and the parabrachial nucleus (PBN). Further, numerous scattered retrogradely labeled neurons were observed in the preoptic area, the ventromedial part of the hypothalamus. the periventricular area, the periaqueductal central gray (CG), the ventrolateral medulla and the dorsal vagal complex. Most of the noradrenergic afferents came from the ventro-lateral medulla (Al group), and only a few from the locus coeruleus complex (A6/A7 groups). A few dopaminergic neurons retrogradely labeled with flurogold were observed in the periventricular area of the hypothalamus. Rare serotoninergic fluorogold labeled neurons belonged to the dorsal raphe nucleus. Most of these afferents came from both sides of the brain, except for hypothalamic supraoptic and paraventricular nuclei. In the light of these anatomical data, we compared our results with data obtained from rats, and we discussed the putative role of these afferents in sheep in the regulation of several specific functions in which the retrochiasmatic area may be involved, such as reproduction.
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Affiliation(s)
- Y Tillet
- Laboratoire de Neuroendocrinologie Sexuelle, INRA-PRMD, Nouzilly, France.
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Ribeiro-Barbosa ER, Skorupa AL, Cipolla-Neto J, Canteras NS. Projections of the basal retrochiasmatic area: a neural site involved in the photic control of pineal metabolism. Brain Res 1999; 839:35-40. [PMID: 10482796 DOI: 10.1016/s0006-8993(99)01685-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
It has been shown that the basal retrochiasmatic area (RCHb), situated immediately ventral to the third ventricle behind the suprachiasmatic nucleus and in front of the arcuate nucleus, is implicated in the nocturnal inhibitory process of melatonin production induced by short-term retinal photo-stimulation. In the present study, the projections of the RCHb have been examined using the Phaseolus vulgaris leucoagglutinin (PHA-L) method in the rat. Considering the putative role of the RCHb in contributing to the short-term photo-inhibition of the pineal gland during the night, it is reasonable to suppose that the RCHb may ultimately inhibit the sympathetic outflow of the upper thoracic segments, known to be critically involved in the control of melatonin secretion. Of particular interest, the present anterograde tract-tracing study indicates all possible paths from the RCHb which may conceivably be involved in influencing the sympathetic outflow and, therefore, melatonin production. Thus, apart from a direct projection to the intermediolateral column at thoracic levels of the spinal cord, the RCHb is in a position to control the sympathetic outflow through other potential routes, such as the dorsal parvicellular part of the paraventricular nucleus of the hypothalamus, lateral hypothalamic area, ventromedial nucleus of the hypothalamus, lateral part of the periaqueductal gray and Barrington's nucleus.
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Affiliation(s)
- E R Ribeiro-Barbosa
- Departamento de Fisiologia e Biofísica, Instituto de Ciências Biomédicas, Universidade de São Paulo, Av. Prof. Lineu Prestes, 1524, São Paulo, Brazil
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