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Aikins AO, Little JT, Rybalchenko N, Cunningham JT. Norepinephrine innervation of the supraoptic nucleus contributes to increased copeptin and dilutional hyponatremia in male rats. Am J Physiol Regul Integr Comp Physiol 2022; 323:R797-R809. [PMID: 36189988 PMCID: PMC9639772 DOI: 10.1152/ajpregu.00086.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Revised: 09/23/2022] [Accepted: 09/23/2022] [Indexed: 11/22/2022]
Abstract
Dilutional hyponatremia associated with liver cirrhosis is due to inappropriate release of arginine vasopressin (AVP). Elevated plasma AVP causes water retention resulting in a decrease in plasma osmolality. Cirrhosis, in this study caused by ligation of the common bile duct (BDL), leads to a decrease in central vascular blood volume and hypotension, stimuli for nonosmotic AVP release. The A1/A2 neurons stimulate the release of AVP from the supraoptic nucleus (SON) in response to nonosmotic stimuli. We hypothesize that the A1/A2 noradrenergic neurons support chronic release of AVP in cirrhosis leading to dilutional hyponatremia. Adult, male rats were anesthetized with 2-3% isoflurane (mixed with 95% O2/5% CO2) and injected in the SON with anti-dopamine β-hydroxylase (DBH) saporin (DSAP) or vehicle followed by either BDL or sham surgery. Plasma copeptin, osmolality, and hematocrit were measured. Brains were processed for ΔFosB, dopamine β-hydroxylase (DBH), and AVP immunohistochemistry. DSAP injection: 1) significantly reduced the number of DBH immunoreactive A1/A2 neurons (A1, P < 0.0001; A2, P = 0.0014), 2) significantly reduced the number of A1/A2 neurons immunoreactive to both DBH and ΔFosB positive neurons (A1, P = 0.0015; A2, P < 0.0001), 3) reduced the number of SON neurons immunoreactive to both AVP and ΔFosB (P < 0.0001), 4) prevented the increase in plasma copeptin observed in vehicle-injected BDL rats (P = 0.0011), and 5) normalized plasma osmolality and hematocrit (plasma osmolality, P = 0.0475; hematocrit, P = 0.0051) as compared with vehicle injection. Our data suggest that A1/A2 neurons contribute to increased plasma copeptin and hypoosmolality in male BDL rats.
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Affiliation(s)
- Ato O Aikins
- Department of Physiology and Anatomy, University of North Texas Health Science Center at Fort Worth, Fort Worth, Texas
| | - Joel T Little
- Department of Physiology and Anatomy, University of North Texas Health Science Center at Fort Worth, Fort Worth, Texas
| | - Nataliya Rybalchenko
- Department of Physiology and Anatomy, University of North Texas Health Science Center at Fort Worth, Fort Worth, Texas
| | - J Thomas Cunningham
- Department of Physiology and Anatomy, University of North Texas Health Science Center at Fort Worth, Fort Worth, Texas
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López-Gambero AJ, Martínez F, Salazar K, Cifuentes M, Nualart F. Brain Glucose-Sensing Mechanism and Energy Homeostasis. Mol Neurobiol 2018; 56:769-796. [PMID: 29796992 DOI: 10.1007/s12035-018-1099-4] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Accepted: 04/25/2018] [Indexed: 01/02/2023]
Abstract
The metabolic and energy state of the organism depends largely on the availability of substrates, such as glucose for ATP production, necessary for maintaining physiological functions. Deregulation in glucose levels leads to the appearance of pathological signs that result in failures in the cardiovascular system and various diseases, such as diabetes, obesity, nephropathy, and neuropathy. Particularly, the brain relies on glucose as fuel for the normal development of neuronal activity. Regions adjacent to the cerebral ventricles, such as the hypothalamus and brainstem, exercise central control in energy homeostasis. These centers house nuclei of neurons whose excitatory activity is sensitive to changes in glucose levels. Determining the different detection mechanisms, the phenotype of neurosecretion, and neural connections involving glucose-sensitive neurons is essential to understanding the response to hypoglycemia through modulation of food intake, thermogenesis, and activation of sympathetic and parasympathetic branches, inducing glucagon and epinephrine secretion and other hypothalamic-pituitary axis-dependent counterregulatory hormones, such as glucocorticoids and growth hormone. The aim of this review focuses on integrating the current understanding of various glucose-sensing mechanisms described in the brain, thereby establishing a relationship between neuroanatomy and control of physiological processes involved in both metabolic and energy balance. This will advance the understanding of increasingly prevalent diseases in the modern world, especially diabetes, and emphasize patterns that regulate and stimulate intake, thermogenesis, and the overall synergistic effect of the neuroendocrine system.
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Affiliation(s)
- A J López-Gambero
- Laboratory of Neurobiology and Stem Cells NeuroCellT, Department of Cellular Biology, Center for Advanced Microscopy CMA BIO BIO, Faculty of Biological Sciences, University of Concepcion, Concepcion, Chile.,Department of Cell Biology, Genetics and Physiology, University of Malaga, IBIMA, BIONAND, Andalusian Center for Nanomedicine and Biotechnology and Networking Research Center on Bioengineering, Biomaterials and Nanomedicine, Málaga, Spain
| | - F Martínez
- Laboratory of Neurobiology and Stem Cells NeuroCellT, Department of Cellular Biology, Center for Advanced Microscopy CMA BIO BIO, Faculty of Biological Sciences, University of Concepcion, Concepcion, Chile
| | - K Salazar
- Laboratory of Neurobiology and Stem Cells NeuroCellT, Department of Cellular Biology, Center for Advanced Microscopy CMA BIO BIO, Faculty of Biological Sciences, University of Concepcion, Concepcion, Chile
| | - M Cifuentes
- Department of Cell Biology, Genetics and Physiology, University of Malaga, IBIMA, BIONAND, Andalusian Center for Nanomedicine and Biotechnology and Networking Research Center on Bioengineering, Biomaterials and Nanomedicine, Málaga, Spain.
| | - F Nualart
- Laboratory of Neurobiology and Stem Cells NeuroCellT, Department of Cellular Biology, Center for Advanced Microscopy CMA BIO BIO, Faculty of Biological Sciences, University of Concepcion, Concepcion, Chile. .,Departamento de Biología Celular, Facultad de Ciencias Biológicas, Universidad de Concepción, Casilla 160-C, Concepción, Chile.
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da Silva EF, Freiria-Oliveira AH, Custódio CHX, Ghedini PC, Bataus LAM, Colombari E, de Castro CH, Colugnati DB, Rosa DA, Cravo SLD, Pedrino GR. A1 noradrenergic neurons lesions reduce natriuresis and hypertensive responses to hypernatremia in rats. PLoS One 2013; 8:e73187. [PMID: 24039883 PMCID: PMC3769347 DOI: 10.1371/journal.pone.0073187] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2013] [Accepted: 07/17/2013] [Indexed: 11/18/2022] Open
Abstract
Noradrenergic neurons in the caudal ventrolateral medulla (CVLM; A1 group) contribute to cardiovascular regulation. The present study assessed whether specific lesions in the A1 group altered the cardiovascular responses that were evoked by hypertonic saline (HS) infusion in non-anesthetized rats. Male Wistar rats (280-340 g) received nanoinjections of antidopamine-β-hydroxylase-saporin (A1 lesion, 0.105 ng.nL(-1)) or free saporin (sham, 0.021 ng.nL(-1)) into their CVLMs. Two weeks later, the rats were anesthetized (2% halothane in O2) and their femoral artery and vein were catheterized and led to exit subcutaneously between the scapulae. On the following day, the animals were submitted to HS infusion (3 M NaCl, 1.8 ml • kg(-1), b.wt., for longer than 1 min). In the sham-group (n = 8), HS induced a sustained pressor response (ΔMAP: 35±3.6 and 11±1.8 mmHg, for 10 and 90 min after HS infusion, respectively; P<0.05 vs. baseline). Ten min after HS infusion, the pressor responses of the anti-DβH-saporin-treated rats (n = 11)were significantly smaller(ΔMAP: 18±1.4 mmHg; P<0.05 vs. baseline and vs. sham group), and at 90 min, their blood pressures reached baseline values (2±1.6 mmHg). Compared to the sham group, the natriuresis that was induced by HS was reduced in the lesioned group 60 min after the challenge (196±5.5 mM vs. 262±7.6 mM, respectively; P<0.05). In addition, A1-lesioned rats excreted only 47% of their sodium 90 min after HS infusion, while sham animals excreted 80% of their sodium. Immunohistochemical analysis confirmed a substantial destruction of the A1 cell group in the CVLM of rats that had been nanoinjected withanti-DβH-saporin. These results suggest that medullary noradrenergic A1 neurons are involved in the excitatory neural pathway that regulates hypertensive and natriuretic responses to acute changes in the composition of body fluid.
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Affiliation(s)
- Elaine Fernanda da Silva
- Department of Physiological Sciences, Biological Sciences Institute, Federal University of Goiás,Goiânia, Goiás, Brazil
| | | | | | - Paulo César Ghedini
- Department of Physiological Sciences, Biological Sciences Institute, Federal University of Goiás,Goiânia, Goiás, Brazil
| | - Luiz Artur Mendes Bataus
- Department of Physiological Sciences, Biological Sciences Institute, Federal University of Goiás,Goiânia, Goiás, Brazil
| | - Eduardo Colombari
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University, Araraquara, São Paulo, Brazil
| | - Carlos Henrique de Castro
- Department of Physiological Sciences, Biological Sciences Institute, Federal University of Goiás,Goiânia, Goiás, Brazil
| | - Diego Basile Colugnati
- Department of Physiological Sciences, Biological Sciences Institute, Federal University of Goiás,Goiânia, Goiás, Brazil
| | - Daniel Alves Rosa
- Department of Physiological Sciences, Biological Sciences Institute, Federal University of Goiás,Goiânia, Goiás, Brazil
| | - Sergio L. D. Cravo
- Department of Physiology, Federal University of São Paulo, São Paulo, São Paulo, Brazil
| | - Gustavo Rodrigues Pedrino
- Department of Physiological Sciences, Biological Sciences Institute, Federal University of Goiás,Goiânia, Goiás, Brazil
- * E-mail:
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Yamashita M, Takayanagi Y, Yoshida M, Nishimori K, Kusama M, Onaka T. Involvement of prolactin-releasing peptide in the activation of oxytocin neurones in response to food intake. J Neuroendocrinol 2013; 25:455-65. [PMID: 23363338 PMCID: PMC3664423 DOI: 10.1111/jne.12019] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2012] [Revised: 12/10/2012] [Accepted: 12/26/2012] [Indexed: 12/16/2022]
Abstract
Food intake activates neurones expressing prolactin-releasing peptide (PrRP) in the medulla oblongata and oxytocin neurones in the hypothalamus. Both PrRP and oxytocin have been shown to have an anorexic action. In the present study, we investigated whether the activation of oxytocin neurones following food intake is mediated by PrRP. We first examined the expression of PrRP receptors (also known as GPR10) in rats. Immunoreactivity of PrRP receptors was observed in oxytocin neurones and in vasopressin neurones in the paraventricular and supraoptic nuclei of the hypothalamus and in the bed nucleus of the stria terminalis. Application of PrRP to isolated supraoptic nuclei facilitated the release of oxytocin and vasopressin. In mice, re-feeding increased the expression of Fos protein in oxytocin neurones of the hypothalamus and bed nucleus of the stria terminalis. The increased expression of Fos protein in oxytocin neurones following re-feeding or i.p. administration of cholecystokinin octapeptide (CCK), a peripheral satiety factor, was impaired in PrRP-deficient mice. CCK-induced oxytocin increase in plasma was also impaired in PrRP-deficient mice. Furthermore, oxytocin receptor-deficient mice showed an increased meal size, as reported in PrRP-deficient mice and in CCKA receptor-deficient mice. These findings suggest that PrRP mediates, at least in part, the activation of oxytocin neurones in response to food intake, and that the CCK-PrRP-oxytocin pathway plays an important role in the control of the termination of each meal.
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Affiliation(s)
- M Yamashita
- Division of Brain and Neurophysiology, Department of Physiology, Jichi Medical University, Shimotsuke-shi, Japan
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Abstract
The magnocellular neurones in the supraoptic nucleus project to the neural lobe and release vasopressin and oxytocin into the peripheral circulation, where they act on the kidney to promote fluid retention or stimulate smooth muscles in the vasculature, uterus and mammary glands to support blood pressure, promote parturition or induce milk let-down, respectively. Hormone release is regulated by complex afferent pathways carrying information about plasma osmolality, blood pressure and volume, cervical stretch, and suckling. These afferent pathways utilise a broad array of neurotransmitters and peptides that activate both ligand-gated ion channels and G-protein coupled receptors (GPCRs). The ligand-gated ion channels induce rapid changes in membrane potential resulting in the generation of action potentials, initiation of exocytosis and the release of hormone into the periphery. By contrast, the GPCRs activate a host of diverse signalling cascades that modulate action potential firing and regulate other cellular functions required to support hormone release (e.g. hormone synthesis, processing, packaging and trafficking). The diversity of these actions is critical for integration of the distinct regulatory signals into a response appropriate for maintaining homeostasis. This review describes several diverse roles of GPCRs in magnocellular neurones, focusing primarily on adrenergic, purinergic and peptidergic (neurokinin and angiotensin) receptors.
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Affiliation(s)
- C D Sladek
- Department of Physiology and Biophysics, University of Colorado School of Medicine, Aurora, CO, USA.
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Geerling JC, Shin JW, Chimenti PC, Loewy AD. Paraventricular hypothalamic nucleus: axonal projections to the brainstem. J Comp Neurol 2010; 518:1460-99. [PMID: 20187136 DOI: 10.1002/cne.22283] [Citation(s) in RCA: 193] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The paraventricular hypothalamic nucleus (PVH) contains many neurons that innervate the brainstem, but information regarding their target sites remains incomplete. Here we labeled neurons in the rat PVH with an anterograde axonal tracer, Phaseolus vulgaris leucoagglutinin (PHAL), and studied their descending projections in reference to specific neuronal subpopulations throughout the brainstem. While many of their target sites were identified previously, numerous new observations were made. Major findings include: 1) In the midbrain, the PVH projects lightly to the ventral tegmental area, Edinger-Westphal nucleus, ventrolateral periaqueductal gray matter, reticular formation, pedunculopontine tegmental nucleus, and dorsal raphe nucleus. 2) In the dorsal pons, the PVH projects heavily to the pre-locus coeruleus, yet very little to the catecholamine neurons in the locus coeruleus, and selectively targets the viscerosensory subregions of the parabrachial nucleus. 3) In the ventral medulla, the superior salivatory nucleus, retrotrapezoid nucleus, compact and external formations of the nucleus ambiguous, A1 and caudal C1 catecholamine neurons, and caudal pressor area receive dense axonal projections, generally exceeding the PVH projection to the rostral C1 region. 4) The medial nucleus of the solitary tract (including A2 noradrenergic and aldosterone-sensitive neurons) receives the most extensive projections of the PVH, substantially more than the dorsal vagal nucleus or area postrema. Our findings suggest that the PVH may modulate a range of homeostatic functions, including cerebral and ocular blood flow, corneal and nasal hydration, ingestive behavior, sodium intake, and glucose metabolism, as well as cardiovascular, gastrointestinal, and respiratory activities.
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Affiliation(s)
- Joel C Geerling
- Department of Anatomy and Neurobiology, Washington University School of Medicine, St Louis, Missouri 63110, USA
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7
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Howe HE, Somponpun SJ, Sladek CD. Role of neurokinin 3 receptors in supraoptic vasopressin and oxytocin neurons. J Neurosci 2005; 24:10103-10. [PMID: 15537880 PMCID: PMC6730173 DOI: 10.1523/jneurosci.3164-04.2004] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Neurokinin 3 receptors (NK3-Rs) are expressed in the supraoptic nucleus (SON), and SON is innervated by substance P (SP)-expressing A1 neurons in the medulla. Because SP stimulates vasopressin (VP) and oxytocin release from explants of the hypothalamo-neurohypophyseal system (HNS), two hypotheses were tested: (1) SP-stimulated VP release is mediated by NK3-Rs, and (2) stimulation of the A1 pathway by hypotension activates SON NK3-Rs. Senktide, an NK3-R agonist, stimulated VP release from HNS explants, but neither a neurokinin 1 receptor antagonist [L732,138 (N-acetyl-L-tryptophan 3,5-bis(tri-fluoromethyl)benzyl ester)] nor two NK3-R antagonists (SB222200 and SB235375) prevented SP-stimulated VP release. Because the affinity of these antagonists for rat NK-Rs may limit their efficacy, NK3-R internalization was used to assess the ability of SP to activate SON NK3-Rs. Senktide, SP, or vehicle was microinjected above SON. The brain was perfused 5 min after injection and stained for NK3-R immunoreactivity. Using confocal microscopy, the number of NK3-R-immunoreactive (-IR) endosomes was counted in a 5.6(2) mu region of cytoplasm in SON neurons. Senktide, but not SP or vehicle, significantly increased the number of NK3-R-IR endosomes in the cytoplasm. When hypotension was induced with hydralazine, NK3-R internalization was observed within 5 min (p < 0.005). A decrease in cytoplasmic NK3-R immunoreactivity was observed within 15 min of hypotension. Unexpectedly, both senktide and hypotension resulted in translocation of NK3-R-IR immunoreactivity to the nucleus. Thus, although these studies do not identify SP as the NK3-R ligand, they do provide evidence for hypotension-induced release of an endogenous tachykinin in SON and evidence suggesting a role for NK3-Rs in transcription regulation.
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MESH Headings
- Acetates/pharmacology
- Animals
- Catecholamines/physiology
- Cell Compartmentation
- Cell Nucleus/chemistry
- Cytoplasm/chemistry
- Endosomes/chemistry
- Hydralazine/pharmacology
- Hypotension/chemically induced
- Hypotension/physiopathology
- Hypothalamo-Hypophyseal System/physiopathology
- Hypothalamus, Anterior/metabolism
- Male
- Microinjections
- Microscopy, Confocal
- Neurons/drug effects
- Neurons/metabolism
- Neurons/ultrastructure
- Oxytocin/metabolism
- Peptide Fragments/pharmacology
- Quinolines/pharmacology
- Rats
- Rats, Sprague-Dawley
- Receptors, G-Protein-Coupled/drug effects
- Receptors, G-Protein-Coupled/physiology
- Receptors, Neurokinin-1/drug effects
- Receptors, Neurokinin-1/physiology
- Receptors, Neurokinin-3/drug effects
- Receptors, Neurokinin-3/physiology
- Substance P/analogs & derivatives
- Substance P/pharmacology
- Tachykinins/physiology
- Transcription, Genetic/drug effects
- Transcription, Genetic/physiology
- Tryptophan/analogs & derivatives
- Tryptophan/pharmacology
- Vasopressins/metabolism
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Affiliation(s)
- Heather E Howe
- Department of Physiology and Biophysics, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA
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Abstract
1. Multiple system atrophy (MSA) is a sporadic neurodegenerative disorder that manifests with parkinsonism, cerebellar ataxia, and autonomic failure in various combinations. 2. Orthostatic hypotension, neurogenic bladder, laryngeal stridor and sleep apnea, and rapid eye movement (REM) sleep behavior disorder are prominent manifestations of MSA. 3. In MSA, there is severe depletion of catecholaminergic neurons of the C1 and A1 areas in the ventrolateral medulla, and this may contribute to orthostatic hypotension and endocrine disturbances in this disorder, respectively. 4. Loss of corticotrophin-releasing factor (CRF) neurons in the pontine micturition area may contribute to neurogenic bladder dysfunction. 5. Respiratory abnormalities may reflect loss of cholinergic neurons in the arcuate nucleus of the ventral medulla. 6. Loss of cholinergic mesopontine neurons, in the setting of loss of locus ceruleus neurons and preservation of rostral raphe neurons, may contribute to REM sleep abnormalities in MSA.
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Affiliation(s)
- Eduardo E Benarroch
- Department of Neurology, Mayo Clinic, 200 First Street SW, Rochester, Minnesota 55905, USA.
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9
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Abstract
The nociceptive and the autonomic systems interact at the level of the periphery, spinal cord, brainstem, and forebrain. Spinal and visceral afferents provide converging information to spinothalamic neurons in the dorsal horn and to neurons of the nucleus tractus solitarius and parabrachial nuclei. These structures project to areas involved in reflex, homeostatic, and behavioral control of autonomic outflow, endocrine function, and nociception. These include monoaminergic cell groups of the medulla and pons, periaqueductal gray, hypothalamus, amygdala, insular cortex, and anterior cingulate gyrus. These interactions should be taken into account to understand the complex pathophysiology of chronic pain disorders.
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Affiliation(s)
- E E Benarroch
- Department of Neurology, Mayo Clinic, Rochester, Minnesota 55905, USA.
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Burbach JP, Luckman SM, Murphy D, Gainer H. Gene regulation in the magnocellular hypothalamo-neurohypophysial system. Physiol Rev 2001; 81:1197-267. [PMID: 11427695 DOI: 10.1152/physrev.2001.81.3.1197] [Citation(s) in RCA: 240] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The hypothalamo-neurohypophysial system (HNS) is the major peptidergic neurosecretory system through which the brain controls peripheral physiology. The hormones vasopressin and oxytocin released from the HNS at the neurohypophysis serve homeostatic functions of water balance and reproduction. From a physiological viewpoint, the core question on the HNS has always been, "How is the rate of hormone production controlled?" Despite a clear description of the physiology, anatomy, cell biology, and biochemistry of the HNS gained over the last 100 years, this question has remained largely unanswered. However, recently, significant progress has been made through studies of gene identity and gene expression in the magnocellular neurons (MCNs) that constitute the HNS. These are keys to mechanisms and events that exist in the HNS. This review is an inventory of what we know about genes expressed in the HNS, about the regulation of their expression in response to physiological stimuli, and about their function. Genes relevant to the central question include receptors and signal transduction components that receive and process the message that the organism is in demand of a neurohypophysial hormone. The key players in gene regulatory events, the transcription factors, deserve special attention. They do not only control rates of hormone production at the level of the gene, but also determine the molecular make-up of the cell essential for appropriate development and physiological functioning. Finally, the HNS neurons are equipped with a machinery to produce and secrete hormones in a regulated manner. With the availability of several gene transfer approaches applicable to the HNS, it is anticipated that new insights will be obtained on how the HNS is able to respond to the physiological demands for its hormones.
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Affiliation(s)
- J P Burbach
- Rudolf Magnus Institute for Neurosciences, Section of Molecular Neuroscience, Department of Medical Pharmacology, University Medical Center Utrecht, Utrecht, The Netherlands.
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Grindstaff RJ, Grindstaff RR, Sullivan MJ, Cunningham JT. Role of the locus ceruleus in baroreceptor regulation of supraoptic vasopressin neurons in the rat. Am J Physiol Regul Integr Comp Physiol 2000; 279:R306-19. [PMID: 10896895 DOI: 10.1152/ajpregu.2000.279.1.r306] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The goal of this study was to identify the source of baroreceptor-related noradrenergic innervation of the diagonal band of Broca (DBB). Male Sprague-Dawley rats underwent sinoaortic denervation (SAD, n = 13) or sham SAD surgery (n = 13). We examined Fos expression produced by baroreceptor activation and dopamine-beta-hydroxylase immunofluorescence in hindbrain regions that contain noradrenergic neurons. Baroreceptors were stimulated by increasing blood pressure >40 mmHg with phenylephrine (10 microgram. kg(-1). min(-1) iv) in sham SAD and SAD rats. Controls were infused with 0.9% saline. Only the locus ceruleus (LC) demonstrated a baroreceptor-dependent increase in Fos immunoreactivity in dopamine-beta-hydroxylase-positive neurons. In a second experiment, normal rats received rhodamine-labeled microsphere injections in the DBB (n = 12) before phenylephrine or vehicle infusion. In these experiments, only the LC consistently contained Fos-positive cells after phenylephrine infusion that were retrogradely labeled from the DBB. Finally, we lesioned the LC with ibotenic acid and obtained extracellular recordings from identified vasopressin neurons in the supraoptic nucleus. LC lesions significantly reduced the number of vasopressin neurons that were inhibited by acute baroreceptor stimulation. Together, these results suggest that noradrenergic neurons in the LC participate in the baroreflex activation of the DBB and may thus be important in the baroreflex inhibition of vasopressin-releasing neurons in the supraoptic nucleus.
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Affiliation(s)
- R J Grindstaff
- Department of Physiology and Dalton Cardiovascular Research Center, University of Missouri-Columbia, Columbia, Missouri 65211, USA
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