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Chen D, Rehfeld JF, Watts AG, Rorsman P, Gundlach AL. History of key regulatory peptide systems and perspectives for future research. J Neuroendocrinol 2023; 35:e13251. [PMID: 37053148 DOI: 10.1111/jne.13251] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/09/2023] [Revised: 02/10/2023] [Accepted: 02/26/2023] [Indexed: 03/06/2023]
Abstract
Throughout the 20th Century, regulatory peptide discovery advanced from the identification of gut hormones to the extraction and characterization of hypothalamic hypophysiotropic factors, and to the isolation and cloning of multiple brain neuropeptides. These discoveries were followed by the discovery of G-protein-coupled and other membrane receptors for these peptides. Subsequently, the systems physiology associated with some of these multiple regulatory peptides and receptors has been comprehensively elucidated and has led to improved therapeutics and diagnostics and their approval by the US Food and Drug Administration. In light of this wealth of information and further potential, it is truly a time of renaissance for regulatory peptides. In this perspective, we review what we have learned from the pioneers in exemplified fields of gut peptides, such as cholecystokinin, enterochromaffin-like-cell peptides, and glucagon, from the trailblazing studies on the key stress hormone, corticotropin-releasing factor, as well as from more recently characterized relaxin-family peptides and receptors. The historical viewpoints are based on our understanding of these topics in light of the earliest phases of research and on subsequent studies and the evolution of knowledge, aiming to sharpen our vision of the current state-of-the-art and those studies that should be prioritized in the future.
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Affiliation(s)
- Duan Chen
- Department of Clinical and Molecular Medicine, Faculty of Medicine and Health Sciences, Norwegian University of Science and Technology (NTNU), Trondheim, Norway
| | - Jens F Rehfeld
- Department of Clinical Biochemistry, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Alan G Watts
- Department of Biological Sciences, Dornsife College of Letters, Arts and Sciences, University of Southern California, Los Angeles, California, USA
| | - Patrik Rorsman
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | - Andrew L Gundlach
- The Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Melbourne, VIC, Australia
- Florey Department of Neuroscience and Mental Health and Department of Anatomy and Physiology, The University of Melbourne, Melbourne, VIC, Australia
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Langhans W, Watts AG, Spector AC. The elusive cephalic phase insulin response: triggers, mechanisms, and functions. Physiol Rev 2023; 103:1423-1485. [PMID: 36422994 PMCID: PMC9942918 DOI: 10.1152/physrev.00025.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Revised: 11/04/2022] [Accepted: 11/20/2022] [Indexed: 11/25/2022] Open
Abstract
The cephalic phase insulin response (CPIR) is classically defined as a head receptor-induced early release of insulin during eating that precedes a postabsorptive rise in blood glucose. Here we discuss, first, the various stimuli that elicit the CPIR and the sensory signaling pathways (sensory limb) involved; second, the efferent pathways that control the various endocrine events associated with eating (motor limb); and third, what is known about the central integrative processes linking the sensory and motor limbs. Fourth, in doing so, we identify open questions and problems with respect to the CPIR in general. Specifically, we consider test conditions that allow, or may not allow, the stimulus to reach the potentially relevant taste receptors and to trigger a CPIR. The possible significance of sweetness and palatability as crucial stimulus features and whether conditioning plays a role in the CPIR are also discussed. Moreover, we ponder the utility of the strict classical CPIR definition based on what is known about the effects of vagal motor neuron activation and thereby acetylcholine on the β-cells, together with the difficulties of the accurate assessment of insulin release. Finally, we weigh the evidence of the physiological and clinical relevance of the cephalic contribution to the release of insulin that occurs during and after a meal. These points are critical for the interpretation of the existing data, and they support a sharper focus on the role of head receptors in the overall insulin response to eating rather than relying solely on the classical CPIR definition.
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Affiliation(s)
- Wolfgang Langhans
- Physiology and Behavior Laboratory, ETH Zürich, Schwerzenbach, Switzerland
| | - Alan G Watts
- Department of Biological Sciences, USC Dornsife College of Letters, Arts and Sciences, University of Southern California, Los Angeles, California
| | - Alan C Spector
- Department of Psychology and Program in Neuroscience, Florida State University, Tallahassee, Florida
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Watts AG, Kanoski SE, Sanchez-Watts G, Langhans W. The physiological control of eating: signals, neurons, and networks. Physiol Rev 2022; 102:689-813. [PMID: 34486393 PMCID: PMC8759974 DOI: 10.1152/physrev.00028.2020] [Citation(s) in RCA: 37] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Accepted: 08/30/2021] [Indexed: 02/07/2023] Open
Abstract
During the past 30 yr, investigating the physiology of eating behaviors has generated a truly vast literature. This is fueled in part by a dramatic increase in obesity and its comorbidities that has coincided with an ever increasing sophistication of genetically based manipulations. These techniques have produced results with a remarkable degree of cell specificity, particularly at the cell signaling level, and have played a lead role in advancing the field. However, putting these findings into a brain-wide context that connects physiological signals and neurons to behavior and somatic physiology requires a thorough consideration of neuronal connections: a field that has also seen an extraordinary technological revolution. Our goal is to present a comprehensive and balanced assessment of how physiological signals associated with energy homeostasis interact at many brain levels to control eating behaviors. A major theme is that these signals engage sets of interacting neural networks throughout the brain that are defined by specific neural connections. We begin by discussing some fundamental concepts, including ones that still engender vigorous debate, that provide the necessary frameworks for understanding how the brain controls meal initiation and termination. These include key word definitions, ATP availability as the pivotal regulated variable in energy homeostasis, neuropeptide signaling, homeostatic and hedonic eating, and meal structure. Within this context, we discuss network models of how key regions in the endbrain (or telencephalon), hypothalamus, hindbrain, medulla, vagus nerve, and spinal cord work together with the gastrointestinal tract to enable the complex motor events that permit animals to eat in diverse situations.
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Affiliation(s)
- Alan G Watts
- The Department of Biological Sciences, Dornsife College of Letters, Arts and Sciences, University of Southern California, Los Angeles, California
| | - Scott E Kanoski
- The Department of Biological Sciences, Dornsife College of Letters, Arts and Sciences, University of Southern California, Los Angeles, California
| | - Graciela Sanchez-Watts
- The Department of Biological Sciences, Dornsife College of Letters, Arts and Sciences, University of Southern California, Los Angeles, California
| | - Wolfgang Langhans
- Physiology and Behavior Laboratory, Eidgenössische Technische Hochschule-Zürich, Schwerzenbach, Switzerland
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4
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Krieger JP, Santos da Conceição EP, Sanchez-Watts G, Arnold M, Pettersen KG, Mohammed M, Modica S, Lossel P, Morrison SF, Madden CJ, Watts AG, Langhans W, Lee SJ. Glucagon-like peptide-1 regulates brown adipose tissue thermogenesis via the gut-brain axis in rats. Am J Physiol Regul Integr Comp Physiol 2018; 315:R708-R720. [PMID: 29847161 DOI: 10.1152/ajpregu.00068.2018] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Endogenous intestinal glucagon-like peptide-1 (GLP-1) controls satiation and glucose metabolism via vagal afferent neurons (VANs). Recently, VANs have received increasing attention for their role in brown adipose tissue (BAT) thermogenesis. It is, however, unclear whether VAN GLP-1 receptor (GLP-1R) signaling affects BAT thermogenesis and energy expenditure (EE) and whether this VAN mechanism contributes to energy balance. First, we tested the effect of the GLP-1R agonist exendin-4 (Ex4, 0.3 μg/kg ip) on EE and BAT thermogenesis and whether these effects require VAN GLP-1R signaling using a rat model with a selective Glp1r knockdown (kd) in VANs. Second, we examined the role of VAN GLP-1R in energy balance during chronic high-fat diet (HFD) feeding in VAN Glp1r kd rats. Finally, we used viral transsynaptic tracers to identify the possible neuronal substrates of such a gut-BAT interaction. VAN Glp1r kd attenuated the acute suppressive effects of Ex4 on EE and BAT thermogenesis. Consistent with this finding, the VAN Glp1r kd increased EE and BAT activity, diminished body weight gain, and improved insulin sensitivity compared with HFD-fed controls. Anterograde transsynaptic viral tracing of VANs infected major hypothalamic and hindbrain areas involved in BAT sympathetic regulation. Moreover, retrograde tracing from BAT combined with laser capture microdissection revealed that a population of VANs expressing Glp1r is synaptically connected to the BAT. Our findings reveal a novel role of VAN GLP-1R signaling in the regulation of EE and BAT thermogenesis and imply that through this gut-brain-BAT connection, intestinal GLP-1 plays a role in HFD-induced metabolic syndrome.
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Affiliation(s)
- Jean-Philippe Krieger
- Physiology and Behavior Laboratory, Eidgenössische Technische Hochschule Zürich, Schwerzenbach, Switzerland
| | | | - Graciela Sanchez-Watts
- Department of Biological Sciences, University of Southern California , Los Angeles, California
| | - Myrtha Arnold
- Physiology and Behavior Laboratory, Eidgenössische Technische Hochschule Zürich, Schwerzenbach, Switzerland
| | - Klaus G Pettersen
- Physiology and Behavior Laboratory, Eidgenössische Technische Hochschule Zürich, Schwerzenbach, Switzerland
| | - Mazher Mohammed
- Department of Neurological Surgery, Oregon Health and Science University , Portland, Oregon
| | - Salvatore Modica
- Translational Nutrition Biology Laboratory, Eidgenössische Technische Hochschule Zürich, Schwerzenbach, Switzerland
| | - Pius Lossel
- Physiology and Behavior Laboratory, Eidgenössische Technische Hochschule Zürich, Schwerzenbach, Switzerland
| | - Shaun F Morrison
- Department of Neurological Surgery, Oregon Health and Science University , Portland, Oregon
| | - Christopher J Madden
- Department of Neurological Surgery, Oregon Health and Science University , Portland, Oregon
| | - Alan G Watts
- Department of Biological Sciences, University of Southern California , Los Angeles, California
| | - Wolfgang Langhans
- Physiology and Behavior Laboratory, Eidgenössische Technische Hochschule Zürich, Schwerzenbach, Switzerland
| | - Shin J Lee
- Physiology and Behavior Laboratory, Eidgenössische Technische Hochschule Zürich, Schwerzenbach, Switzerland
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Langhans W, Adan R, Arnold M, Banks WA, Card JP, Dailey MJ, Daniels D, de Kloet AD, de Lartigue G, Dickson S, Fedele S, Grill HJ, Jansson JO, Kaufman S, Kolar G, Krause E, Lee SJ, Le Foll C, Levin BE, Lutz TA, Mansouri A, Moran TH, Pacheco-López G, Ramachandran D, Raybould H, Rinaman L, Samson WK, Sanchez-Watts G, Seeley RJ, Skibicka KP, Small D, Spector AC, Tamashiro KL, Templeton B, Trapp S, Tso P, Watts AG, Weissfeld N, Williams D, Wolfrum C, Yosten G, Woods SC. New horizons for future research - Critical issues to consider for maximizing research excellence and impact. Mol Metab 2018; 14:53-59. [PMID: 29886182 PMCID: PMC6034110 DOI: 10.1016/j.molmet.2018.05.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Revised: 05/08/2018] [Accepted: 05/08/2018] [Indexed: 12/18/2022] Open
Affiliation(s)
- Wolfgang Langhans
- Physiology and Behavior Laboratory, ETH Zurich, Schorenstr. 16, 8603, Schwerzenbach, Switzerland.
| | - Roger Adan
- Brain Center Rudolf Magnus, Dept. of Translational Neuroscience, University Medical Center Utrecht, Utrecht University, Utrecht, 3584, CG, The Netherlands; Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Sweden
| | - Myrtha Arnold
- Physiology and Behavior Laboratory, ETH Zurich, Schorenstr. 16, 8603, Schwerzenbach, Switzerland
| | - William A Banks
- Geriatric Research Education and Clinical Center, Veterans Affairs Puget Sound Health Care System, Seattle, WA, USA; Division of Gerontology and Geriatric Medicine, Department of Medicine, University of Washington School of Medicine, Seattle, WA, USA
| | - J Patrick Card
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, PA, 15260, USA
| | - Megan J Dailey
- Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Derek Daniels
- Behavioral Neuroscience Program, Department of Psychology, State University of New York at Buffalo, Buffalo, NY 14260, USA
| | - Annette D de Kloet
- Department of Physiology and Functional Genomics, College of Medicine, University of Florida, Gainesville, FL, 32611, USA
| | - Guillaume de Lartigue
- The John B. Pierce Laboratory, New Haven, CT, 06519, USA; Department of Cellular and Molecular Physiology, Yale Medical School, New Haven, CT, 06519, USA
| | - Suzanne Dickson
- Dept Physiology/Endocrine, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at the University of Gothenburg, Medicinaregatan 11, SE-405 30, Gothenburg, Sweden
| | - Shahana Fedele
- Physiology and Behavior Laboratory, ETH Zurich, Schorenstr. 16, 8603, Schwerzenbach, Switzerland
| | - Harvey J Grill
- Lynch Laboratories University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - John-Olov Jansson
- Dept Physiology/Endocrine, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at the University of Gothenburg, Medicinaregatan 11, SE-405 30, Gothenburg, Sweden
| | - Sharon Kaufman
- Physiology and Behavior Laboratory, ETH Zurich, Schorenstr. 16, 8603, Schwerzenbach, Switzerland
| | - Grant Kolar
- Pathology, Saint Louis University School of Medicine, St. Louis, MO, 63104, USA
| | - Eric Krause
- Department of Pharmacodynamics, College of Pharmacy, University of Florida, 32611, USA
| | - Shin J Lee
- Physiology and Behavior Laboratory, ETH Zurich, Schorenstr. 16, 8603, Schwerzenbach, Switzerland
| | - Christelle Le Foll
- Institute of Veterinary Physiology, University of Zurich, Winterthurerstrasse 260, CH 8057, Zurich, Switzerland
| | - Barry E Levin
- Department of Neurology, Rutgers, New Jersey Medical School, Newark, NJ, 07103, USA
| | - Thomas A Lutz
- Institute of Veterinary Physiology, University of Zurich, Winterthurerstrasse 260, CH 8057, Zurich, Switzerland
| | - Abdelhak Mansouri
- Physiology and Behavior Laboratory, ETH Zurich, Schorenstr. 16, 8603, Schwerzenbach, Switzerland
| | - Timothy H Moran
- Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Gustavo Pacheco-López
- Metropolitan Autonomous University (UAM), Campus Lerma, Health Sciences Department, Lerma, Edo Mex, 52005, Mexico
| | - Deepti Ramachandran
- Physiology and Behavior Laboratory, ETH Zurich, Schorenstr. 16, 8603, Schwerzenbach, Switzerland
| | - Helen Raybould
- Dept. of Anatomy, Physiology and Cell Biology, UC Davis School of Veterinary Medicine, Davis, CA, 95616, USA
| | - Linda Rinaman
- Florida State University, Dept. of Psychology, Tallahassee, FL, 32303, USA
| | - Willis K Samson
- Pharmacology and Physiology, Saint Louis University School of Medicine, St. Louis, MO, 63104, USA
| | - Graciela Sanchez-Watts
- The Department of Biological Sciences, USC Dornsife College of Letters, Arts & Sciences, University of Southern California, Los Angeles, CA 90089, USA
| | - Randy J Seeley
- Departments of Surgery, Internal Medicine and Nutritional Science, University of Michigan, Ann Arbor, MI 48109, USA
| | - Karolina P Skibicka
- Department of Physiology/Metabolic Physiology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at the University of Gothenburg, SE-405 30 Gothenburg, Sweden; Wallenberg Centre for Molecular and Translational Medicine, University of Gothenburg, Sweden
| | - Dana Small
- Yale University School of Medicine, The Modern Diet and Physiology Research Center, New Haven, CT 06511, USA
| | - Alan C Spector
- Department of Psychology and Program in Neuroscience, Florida State University, Tallahassee, FL, 32306, USA
| | - Kellie L Tamashiro
- Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Brian Templeton
- Midwest Community Fundraising, Inc., Cincinnati, OH, 45223, USA
| | - Stefan Trapp
- Centre for Cardiovascular and Metabolic Neuroscience; Department of Neuroscience, Physiology & Pharmacology, UCL, London WC1E 6BT, UK
| | - Patrick Tso
- Department of Pathology and Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, OH, 45237, USA
| | - Alan G Watts
- The Department of Biological Sciences, USC Dornsife College of Letters, Arts & Sciences, University of Southern California, Los Angeles, CA 90089, USA
| | - Nadja Weissfeld
- Physiology and Behavior Laboratory, ETH Zurich, Schorenstr. 16, 8603, Schwerzenbach, Switzerland
| | - Diana Williams
- Department of Psychology and Program in Neuroscience, Florida State University, Tallahassee, FL, 32306, USA
| | - Christian Wolfrum
- Translational Nutrition Biology Laboratory, ETH Zurich, 8603, Schwerzenbach, Switzerland
| | - Gina Yosten
- Pharmacology and Physiology, Saint Louis University School of Medicine, St. Louis, MO, 63104, USA
| | - Stephen C Woods
- Department of Psychiatry and Behavioral Neuroscience, University of Cincinnati School of Medicine, Cincinnati, OH, 45237, USA
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Lee SJ, Sanchez-Watts G, Krieger JP, Pignalosa A, Norell PN, Cortella A, Pettersen KG, Vrdoljak D, Hayes MR, Kanoski SE, Langhans W, Watts AG. Loss of dorsomedial hypothalamic GLP-1 signaling reduces BAT thermogenesis and increases adiposity. Mol Metab 2018; 11:33-46. [PMID: 29650350 PMCID: PMC6001878 DOI: 10.1016/j.molmet.2018.03.008] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Revised: 03/09/2018] [Accepted: 03/14/2018] [Indexed: 12/15/2022] Open
Abstract
Objective Glucagon-like peptide-1 (GLP-1) neurons in the hindbrain densely innervate the dorsomedial hypothalamus (DMH), a nucleus strongly implicated in body weight regulation and the sympathetic control of brown adipose tissue (BAT) thermogenesis. Therefore, DMH GLP-1 receptors (GLP-1R) are well placed to regulate energy balance by controlling sympathetic outflow and BAT function. Methods We investigate this possibility in adult male rats by using direct administration of GLP-1 (0.5 ug) into the DMH, knocking down DMH GLP-1R mRNA with viral-mediated RNA interference, and by examining the neurochemical phenotype of GLP-1R expressing cells in the DMH using in situ hybridization. Results GLP-1 administered into the DMH increased BAT thermogenesis and hepatic triglyceride (TG) mobilization. On the other hand, Glp1r knockdown (KD) in the DMH increased body weight gain and adiposity, with a concomitant reduction in energy expenditure (EE), BAT temperature, and uncoupling protein 1 (UCP1) expression. Moreover, DMH Glp1r KD induced hepatic steatosis, increased plasma TG, and elevated liver specific de-novo lipogenesis, effects that collectively contributed to insulin resistance. Interestingly, DMH Glp1r KD increased neuropeptide Y (NPY) mRNA expression in the DMH. GLP-1R mRNA in the DMH, however, was found in GABAergic not NPY neurons, consistent with a GLP-1R-dependent inhibition of NPY neurons that is mediated by local GABAergic neurons. Finally, DMH Glp1r KD attenuated the anorexigenic effects of the GLP-1R agonist exendin-4, highlighting an important role of DMH GLP-1R signaling in GLP-1-based therapies. Conclusions Collectively, our data show that DMH GLP-1R signaling plays a key role for BAT thermogenesis and adiposity. DMH GLP-1R stimulation acutely increases BAT thermogenesis. DMH GLP-1R mRNA knockdown decreases EE and BAT thermogenesis. DMH GLP-1R mRNA knockdown impairs lipid and glucose metabolism. Reduced DMH GLP-1R signaling blunts the anorexigenic responses to Ex-4. DMH GLP-1R signaling indirectly regulates NPY gene expression.
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Affiliation(s)
- Shin J Lee
- Physiology and Behavior Laboratory, ETH Zürich, 8603 Schwerzenbach, Switzerland.
| | - Graciela Sanchez-Watts
- Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA
| | | | - Angelica Pignalosa
- Physiology and Behavior Laboratory, ETH Zürich, 8603 Schwerzenbach, Switzerland
| | - Puck N Norell
- Physiology and Behavior Laboratory, ETH Zürich, 8603 Schwerzenbach, Switzerland
| | - Alyssa Cortella
- Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA
| | - Klaus G Pettersen
- Physiology and Behavior Laboratory, ETH Zürich, 8603 Schwerzenbach, Switzerland
| | - Dubravka Vrdoljak
- Physiology and Behavior Laboratory, ETH Zürich, 8603 Schwerzenbach, Switzerland
| | - Matthew R Hayes
- Department of Psychiatry, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
| | - Scott E Kanoski
- Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA
| | - Wolfgang Langhans
- Physiology and Behavior Laboratory, ETH Zürich, 8603 Schwerzenbach, Switzerland
| | - Alan G Watts
- Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA
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Johnson CS, Bains JS, Watts AG. Neurotransmitter diversity in pre-synaptic terminals located in the parvicellular neuroendocrine paraventricular nucleus of the rat and mouse hypothalamus. J Comp Neurol 2018; 526:1287-1306. [PMID: 29424419 DOI: 10.1002/cne.24407] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2017] [Revised: 01/24/2018] [Accepted: 01/25/2018] [Indexed: 02/02/2023]
Abstract
Virtually all rodent neuroendocrine corticotropin-releasing-hormone (CRH) neurons are in the dorsal medial parvicellular (mpd) part of the paraventricular nucleus of the hypothalamus (PVH). They form the final common pathway for adrenocortical stress responses. Their activity is controlled by sets of GABA-, glutamate-, and catecholamine-containing inputs arranged in an interactive pre-motor network. Defining the nature and arrangement of these inputs can help clarify how stressor type and intensity information is conveyed to neuroendocrine neurons. Here we use immunohistochemistry with high-resolution 3-dimensional image analyses to examine the arrangement of single- and co-occurring GABA, glutamate, and catecholamine markers in synaptophysin-defined pre-synaptic terminals in the PVHmpd of unstressed rats and Crh-IRES-Cre;Ai14 transgenic mice: respectively, vesicular glutamate transporter 2 (VGluT2), vesicular GABA transporter (VGAT), dopamine β-hydroxylase (DBH), and phenylethanolamine n-methyltransferase (PNMT). Just over half of all PVHmpd pre-synaptic terminals contain VGAT, with slightly less containing VGluT2. The vast majority of terminal appositions with mouse CRH neurons occur non-somatically. However, there are significantly more somatic VGAT than VGluT2 appositions. In the rat PVHmpd, about five times as many pre-synaptic terminals contain PNMT than DBH only. However, because epinephrine release has never been detected in the PVH, PNMT terminals may functionally be noradrenergic not adrenergic. PNMT and VGluT2 co-occur in some pre-synaptic terminals indicating the potential for co-transmission of glutamate and norepinephrine. Collectively, these results provide a structural basis for how GABA/glutamate/catecholamine interactions enable adrenocortical responses to fast-onset interosensory stimuli, and more broadly, how combinations of PVH neurotransmitters and neuromodulators interact dynamically to control adrenocortical activity.
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Affiliation(s)
- Caroline S Johnson
- The Department of Biological Sciences, USC Dornsife College of Letters, Arts, and Sciences, and Neuroscience, Graduate Program, University of Southern California, Los Angeles, California
| | - Jaideep S Bains
- Hotchkiss Brain Institute, Department of Physiology and Pharmacology, University of Calgary, Alberta, Canada
| | - Alan G Watts
- The Department of Biological Sciences, USC Dornsife College of Letters, Arts, and Sciences, and Neuroscience, Graduate Program, University of Southern California, Los Angeles, California
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8
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Lee SJ, Jokiaho AJ, Sanchez-Watts G, Watts AG. Catecholaminergic projections into an interconnected forebrain network control the sensitivity of male rats to diet-induced obesity. Am J Physiol Regul Integr Comp Physiol 2018; 314:R811-R823. [PMID: 29384699 DOI: 10.1152/ajpregu.00423.2017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Hindbrain catecholamine neurons convey gut-derived metabolic signals to an interconnected neuronal network in the hypothalamus and adjacent forebrain. These neurons are critical for short-term glycemic control, glucocorticoid and glucoprivic feeding responses, and glucagon-like peptide 1 (GLP-1) signaling. Here we investigate whether these pathways also contribute to long-term energy homeostasis by controlling obesogenic sensitivity to a high-fat/high-sucrose choice (HFSC) diet. We ablated hindbrain-originating catecholaminergic projections by injecting anti-dopamine-β-hydroxylase-conjugated saporin (DSAP) into the paraventricular nucleus of the hypothalamus (PVH) of male rats fed a chow diet for up to 12 wk or a HFSC diet for 8 wk. We measured the effects of DSAP lesions on food choices; visceral adiposity; plasma glucose, insulin, and leptin; and indicators of long-term ACTH and corticosterone secretion. We also determined lesion effects on the number of carbohydrate or fat calories required to increase visceral fat. Finally, we examined corticotropin-releasing hormone levels in the PVH and arcuate nucleus expression of neuropeptide Y ( Npy), agouti-related peptide ( Agrp), and proopiomelanocortin ( Pomc). DSAP-injected chow-fed rats slowly increase visceral adiposity but quickly develop mild insulin resistance and elevated blood glucose. DSAP-injected HFSC-fed rats, however, dramatically increase food intake, body weight, and visceral adiposity beyond the level in control HFSC-fed rats. These changes are concomitant with 1) a reduction in the number of carbohydrate calories required to generate visceral fat, 2) abnormal Npy, Agrp, and Pomc expression, and 3) aberrant control of insulin secretion and glucocorticoid negative feedback. Long-term metabolic adaptations to high-carbohydrate diets, therefore, require intact forebrain catecholamine projections. Without them, animals cannot alter forebrain mechanisms to restrain increased visceral adiposity.
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Affiliation(s)
- Shin J Lee
- Physiology and Behavior Laboratory, ETH Zürich, Schwerzenbach, Switzerland
| | - Anne J Jokiaho
- Department of Biological Sciences, Dana and David Dornsife College of Letters, Arts and Sciences, University of Southern California , Los Angeles, California
| | - Graciela Sanchez-Watts
- Department of Biological Sciences, Dana and David Dornsife College of Letters, Arts and Sciences, University of Southern California , Los Angeles, California
| | - Alan G Watts
- Physiology and Behavior Laboratory, ETH Zürich, Schwerzenbach, Switzerland.,Department of Biological Sciences, Dana and David Dornsife College of Letters, Arts and Sciences, University of Southern California , Los Angeles, California
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Abstract
Real-time activity measurements of genetically identified neuroendocrine vasopressin neurons show they can anticipate osmotic challenges. In this issue of Neuron, Mandelblat-Cerf et al. (2017) show that correlating these results with ongoing behavior and plasma osmolality points to the existence of brain networks that integrate exterosensory cues with interosensory signals to drive neuroendocrine output.
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Affiliation(s)
- Alan G Watts
- Department of Biological Sciences, Dornsife College of Letters, Arts and Sciences, The University of Southern California, Los Angeles, CA 90089, USA.
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Ryu V, Watts AG, Xue B, Bartness TJ. Bidirectional crosstalk between the sensory and sympathetic motor systems innervating brown and white adipose tissue in male Siberian hamsters. Am J Physiol Regul Integr Comp Physiol 2017; 312:R324-R337. [PMID: 28077392 DOI: 10.1152/ajpregu.00456.2015] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Revised: 11/28/2016] [Accepted: 12/31/2016] [Indexed: 01/31/2023]
Abstract
The brain networks connected to the sympathetic motor and sensory innervations of brown (BAT) and white (WAT) adipose tissues were originally described using two transneuronally transported viruses: the retrogradely transported pseudorabies virus (PRV), and the anterogradely transported H129 strain of herpes simplex virus-1 (HSV-1 H129). Further complexity was added to this network organization when combined injections of PRV and HSV-1 H129 into either BAT or WAT of the same animal generated sets of coinfected neurons in the brain, spinal cord, and sympathetic and dorsal root ganglia. These neurons are well positioned to act as sensorimotor links in the feedback circuits that control each fat pad. We have now determined the extent of sensorimotor crosstalk between interscapular BAT (IBAT) and inguinal WAT (IWAT). PRV152 and HSV-1 H129 were each injected into IBAT or IWAT of the same animal: H129 into IBAT and PRV152 into IWAT. The reverse configuration was applied in a different set of animals. We found single-labeled neurons together with H129+PRV152 coinfected neurons in multiple brain sites, with lesser numbers in the sympathetic and dorsal root ganglia that innervate IBAT and IWAT. We propose that these coinfected neurons mediate sensory-sympathetic motor crosstalk between IBAT and IWAT. Comparing the relative numbers of coinfected neurons between the two injection configurations showed a bias toward IBAT-sensory and IWAT-sympathetic motor feedback loops. These coinfected neurons provide a neuroanatomical framework for functional interactions between IBAT thermogenesis and IWAT lipolysis that occurs with cold exposure, food restriction/deprivation, exercise, and more generally with alterations in adiposity.
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Affiliation(s)
- Vitaly Ryu
- Department of Biology, Obesity Reversal Center, Georgia State University, Atlanta, Georgia; and
| | - Alan G Watts
- Department of Biological Sciences, University of Southern California, Dornsife College of Letters, Arts, and Sciences, University of Southern California, Los Angeles, California
| | - Bingzhong Xue
- Department of Biology, Obesity Reversal Center, Georgia State University, Atlanta, Georgia; and
| | - Timothy J Bartness
- Department of Biology, Obesity Reversal Center, Georgia State University, Atlanta, Georgia; and
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11
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Lee SJ, Diener K, Kaufman S, Krieger JP, Pettersen KG, Jejelava N, Arnold M, Watts AG, Langhans W. Limiting glucocorticoid secretion increases the anorexigenic property of Exendin-4. Mol Metab 2016; 5:552-565. [PMID: 27408779 PMCID: PMC4921942 DOI: 10.1016/j.molmet.2016.04.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Revised: 04/14/2016] [Accepted: 04/27/2016] [Indexed: 12/25/2022] Open
Abstract
Objective Glucagon-like peptide-1 (GLP-1) analogs are attractive options for the treatment of type II diabetes and obesity because of their incretin and anorexigenic effects. Peripheral administration of the GLP-1R agonist Exendin-4 (Ex-4) also increases glucocorticoid secretion in rodents and humans, but whether the released glucocorticoids interact with Ex-4's anorexigenic effect remains unclear. Methods To test this, we used two experimental approaches that suppress corticosterone secretion and then assessed Ex-4 effects on eating in adult male rats. First, we combined acute and chronic low dose dexamethasone treatment with Ex-4. Second, we ablated hindbrain catecholamine neurons projecting to the hypothalamus with anti-dopamine-β-hydroxylase-saporin (DSAP) to block Ex-4-induced corticosterone secretion. Results Combining dexamethasone and Ex-4 produced a larger acute anorexigenic effect than Ex-4 alone. Likewise, chronic dexamethasone and Ex-4 co-treatment produced a synergistic effect on eating and greater body weight loss in diet-induced obese rats than Ex-4 alone. DSAP lesions not only blunted Ex-4's ability to increase corticosterone secretion, but potentiated the anorexigenic effect of Ex-4, indicating that Ex-4-dependent corticosterone secretion opposes Ex-4's actions. Consistent with the enhancement of Ex-4's anorexigenic effect, DSAP lesion altered Ex-4-dependent changes in neuropeptide Y, preproglucagon, and corticotropin releasing hormone gene expression involved in glucocorticoid feedback. Conclusions Our findings demonstrate that limiting glucocorticoid secretion and actions with low dose dexamethasone or DSAP lesion increases Ex-4's ability to reduce food intake and body weight. Novel glucocorticoid receptor based mechanisms, therefore, may help enhance GLP-1-based obesity therapies. Blocking HPA axis by low dose dexamethasone increased the anorexigenic property of Ex-4. Dexamethasone/Ex-4 co-treatment reduced food intake and body weight in diet-induced obese rats more than Ex-4 alone. A brain lesion model identified a potential central interaction between glucocorticoids and GLP-1 in food intake control.
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Affiliation(s)
- Shin J Lee
- Physiology and Behavior Laboratory, ETH Zürich, 8603 Schwerzenbach, Switzerland.
| | - Katharina Diener
- Physiology and Behavior Laboratory, ETH Zürich, 8603 Schwerzenbach, Switzerland
| | - Sharon Kaufman
- Physiology and Behavior Laboratory, ETH Zürich, 8603 Schwerzenbach, Switzerland
| | | | - Klaus G Pettersen
- Physiology and Behavior Laboratory, ETH Zürich, 8603 Schwerzenbach, Switzerland
| | - Nino Jejelava
- Physiology and Behavior Laboratory, ETH Zürich, 8603 Schwerzenbach, Switzerland
| | - Myrtha Arnold
- Physiology and Behavior Laboratory, ETH Zürich, 8603 Schwerzenbach, Switzerland
| | - Alan G Watts
- Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA
| | - Wolfgang Langhans
- Physiology and Behavior Laboratory, ETH Zürich, 8603 Schwerzenbach, Switzerland
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Foster NN, Azam S, Watts AG. Rapid-onset hypoglycemia suppresses Fos expression in discrete parts of the ventromedial nucleus of the hypothalamus. Am J Physiol Regul Integr Comp Physiol 2016; 310:R1177-85. [PMID: 27030665 DOI: 10.1152/ajpregu.00042.2016] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Accepted: 03/23/2016] [Indexed: 01/12/2023]
Abstract
The consensus view of the ventromedial nucleus of the hypothalamus (VMH) is that it is a key node in the rodent brain network controlling sympathoadrenal counterregulatory responses to hypoglycemia. To identify the location of hypoglycemia-responsive neurons in the VMH, we performed a high spatial resolution Fos analysis in the VMH of rats made hypoglycemic with intraperitoneal injections of insulin. We examined Fos expression in the four constituent parts of VMH throughout its rostrocaudal extent and determined their relationship to blood glucose concentrations. Hypoglycemia significantly decreased Fos expression only in the dorsomedial and central parts of the VMH, but not its anterior or ventrolateral parts. Moreover, the number of Fos-expressing neurons was significantly and positively correlated in the two responsive regions with terminal blood glucose concentrations. We also measured Fos responses in the paraventricular nucleus of the hypothalamus (PVH) and in several levels of the periaqueductal gray (PAG), which receives strong projections from the VMH. We found the expected and highly significant increase in Fos in the neuroendocrine PVH, which was negatively correlated to terminal blood glucose concentrations, but no significant differences were seen in any part of the PAG. Our results show that there are distinct populations of VMH neurons whose Fos expression is suppressed by hypoglycemia, and their numbers correlate with blood glucose. These findings support a clear division of glycemic control functions within the different parts of the VMH.
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Affiliation(s)
- Nicholas N Foster
- Department of Biological Sciences, USC Dornsife College of Letters, Arts, and Sciences, University of Southern California, Los Angeles, California
| | - Sana Azam
- Department of Biological Sciences, USC Dornsife College of Letters, Arts, and Sciences, University of Southern California, Los Angeles, California
| | - Alan G Watts
- Department of Biological Sciences, USC Dornsife College of Letters, Arts, and Sciences, University of Southern California, Los Angeles, California
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13
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Watts AG, Grill HJ. Tim Bartness (1953-2015). Am J Physiol Regul Integr Comp Physiol 2016; 310:R385-7. [PMID: 26843579 DOI: 10.1152/ajpregu.00036.2016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Alan G Watts
- Department of Biological Sciences, University of Southern California, Los Angeles, California; and
| | - Harvey J Grill
- Department of Psychology, Univeristy of Pennsylvania, Philadelphia, Pennsylvania
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14
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Abstract
In November 1955, Geoffrey Harris published a paper based on the Christian A Herter Lecture he had given earlier that year at Johns Hopkins University in Baltimore, MD, USA. The paper reviewed the contemporary research that was starting to explain how the hypothalamus controlled the pituitary gland. In the process of doing so, Harris introduced a set of properties that helped define the neuroendocrine hypothalamus. They included: i) three criteria that putative releasing factors for adenohypophysial hormones would have to fulfill; ii) an analogy between the representation of body parts in the sensory and motor cortices and the spatial localization of neuroendocrine function in the hypothalamus; and iii) the idea that neuroendocrine neurons are motor neurons and the pituitary stalk functions as a Sherringtonian final common pathway through which the impact of sensory and emotional events on neuroendocrine neurons must pass in order to control pituitary hormone release. Were these properties a sign that the major neuroscientific discoveries that were being made in the early 1950s were beginning to influence neuroendocrinology? This Thematic Review discusses two main points: the context and significance of Harris's Herter Lecture for how our understanding of neuroendocrine anatomy (particularly as it relates to the control of the adenohypophysis) has developed since 1955; and, within this framework, how novel and powerful techniques are currently taking our understanding of the structure of the neuroendocrine hypothalamus to new levels.
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Affiliation(s)
- Alan G Watts
- Department of Biological SciencesUSC Dornsife College of Letters, Arts, and Sciences, University of Southern California, Hedco Neuroscience Building, MC 2520, Los Angeles, California 90089-2520, USA
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15
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Abstract
Hypoglycemia poses a serious threat to the integrity of the brain, owing to its reliance on blood glucose as a fuel. Protecting against hypoglycemia is an extended network of glucose sensors located within the brain and in the periphery that serve to mediate responses restoring euglycemia, i.e., counterregulatory responses. This review examines the various glucose sensory loci involved in hypoglycemic detection, with a particular emphasis on peripheral glucose sensory loci and their contribution to hypoglycemic counterregulation.
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Affiliation(s)
- Casey M Donovan
- Department of Biological Sciences, The Center for NeuroMetabolic Interactions, USC Dornsife College of Letters, Arts and Sciences, University of Southern California, Los Angeles, California
| | - Alan G Watts
- Department of Biological Sciences, The Center for NeuroMetabolic Interactions, USC Dornsife College of Letters, Arts and Sciences, University of Southern California, Los Angeles, California
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16
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Watts AG, Bezanson L, McCarthy J. The international symposia on career development and public policy: Retrospect and prospect. Australian Journal of Career Development 2014. [DOI: 10.1177/1038416214543390] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Between 1999 and 2011, seven international symposia on career development and public policy were held at various venues across the world, and an International Centre was established to support and maintain continuity between these events. These developments were closely intertwined with a number of other significant international developments. The origins of the symposia are described; their core design features are defined; their evolution is outlined and reviewed; and their impact is assessed. This article concludes with a discussion of the prospects for future symposia and for the International Centre.
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Affiliation(s)
- AG Watts
- International Centre for Guidance Studies, University of Derby, UK
| | | | - John McCarthy
- International Centre for Career Development and Public Policy, France
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Bohland M, Matveyenko AV, Saberi M, Khan AM, Watts AG, Donovan CM. Activation of hindbrain neurons is mediated by portal-mesenteric vein glucosensors during slow-onset hypoglycemia. Diabetes 2014; 63:2866-75. [PMID: 24727435 PMCID: PMC4113064 DOI: 10.2337/db13-1600] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Hypoglycemic detection at the portal-mesenteric vein (PMV) appears mediated by spinal afferents and is critical for the counter-regulatory response (CRR) to slow-onset, but not rapid-onset, hypoglycemia. Since rapid-onset hypoglycemia induces Fos protein expression in discrete brain regions, we hypothesized that denervation of the PMV or lesioning spinal afferents would suppress Fos expression in the dorsal medulla during slow-onset hypoglycemia, revealing a central nervous system reliance on PMV glucosensors. Rats undergoing PMV deafferentation via capsaicin, celiac-superior mesenteric ganglionectomy (CSMG), or total subdiaphragmatic vagotomy (TSV) were exposed to hyperinsulinemic-hypoglycemic clamps where glycemia was lowered slowly over 60-75 min. In response to hypoglycemia, control animals demonstrated a robust CRR along with marked Fos expression in the area postrema, nucleus of the solitary tract, and dorsal motor nucleus of the vagus. Fos expression was suppressed by 65-92% in capsaicin-treated animals, as was epinephrine (74%), norepinephrine (33%), and glucagon (47%). CSMG also suppressed Fos expression and CRR during slow-onset hypoglycemia, whereas TSV failed to impact either. In contrast, CSMG failed to impact upon Fos expression or the CRR during rapid-onset hypoglycemia. Peripheral glucosensory input from the PMV is therefore required for activation of hindbrain neurons and the full CRR during slow-onset hypoglycemia.
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Affiliation(s)
- MaryAnn Bohland
- Department of Biological Sciences and Center for NeuroMetabolic Interactions, University of Southern California, Los Angeles, CA
| | - Aleksey V Matveyenko
- Department of Biological Sciences and Center for NeuroMetabolic Interactions, University of Southern California, Los Angeles, CA
| | - Maziyar Saberi
- Department of Biological Sciences and Center for NeuroMetabolic Interactions, University of Southern California, Los Angeles, CA
| | - Arshad M Khan
- Department of Biological Sciences and Center for NeuroMetabolic Interactions, University of Southern California, Los Angeles, CA
| | - Alan G Watts
- Department of Biological Sciences and Center for NeuroMetabolic Interactions, University of Southern California, Los Angeles, CA
| | - Casey M Donovan
- Department of Biological Sciences and Center for NeuroMetabolic Interactions, University of Southern California, Los Angeles, CA
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18
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Jokiaho AJ, Donovan CM, Watts AG. The rate of fall of blood glucose determines the necessity of forebrain-projecting catecholaminergic neurons for male rat sympathoadrenal responses. Diabetes 2014; 63:2854-65. [PMID: 24740574 PMCID: PMC4113074 DOI: 10.2337/db13-1753] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Different onset rates of insulin-induced hypoglycemia use distinct glucosensors to activate sympathoadrenal counterregulatory responses (CRRs). Glucosensory elements in the portal-mesenteric veins are dispensable with faster rates when brain elements predominate, but are essential for responses to the slower-onset hypoglycemia that is common with insulin therapy. Whether a similar rate-associated divergence exists within more expansive brain networks is unknown. Hindbrain catecholamine neurons distribute glycemia-related information throughout the forebrain. We tested in male rats whether catecholaminergic neurons that project to the medial and ventromedial hypothalamus are required for sympathoadrenal CRRs to rapid- and slow-onset hypoglycemia and whether these neurons are differentially engaged as onset rates change. Using a catecholamine-specific neurotoxin and hyperinsulinemic-hypoglycemic clamps, we found that sympathoadrenal CRRs to slow- but not rapid-onset hypoglycemia require hypothalamus-projecting catecholaminergic neurons, the majority of which originate in the ventrolateral medulla. As determined with Fos, these neurons are differentially activated by the two onset rates. We conclude that 1) catecholaminergic projections to the hypothalamus provide essential information for activating sympathoadrenal CRRs to slow- but not rapid-onset hypoglycemia, 2) hypoglycemia onset rates have a major impact on the hypothalamic mechanisms that enable sympathoadrenal CRRs, and 3) hypoglycemia-related sensory information activates hindbrain catecholaminergic neurons in a rate-dependent manner.
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Affiliation(s)
- Anne J Jokiaho
- Center for NeuroMetabolic Interactions, The Integrated and Evolutionary Biology Graduate Program, and The Department of Biological Sciences, USC Dornsife College of Letters, Arts, and Sciences, University of Southern California, Los Angeles, CA
| | - Casey M Donovan
- Center for NeuroMetabolic Interactions, The Integrated and Evolutionary Biology Graduate Program, and The Department of Biological Sciences, USC Dornsife College of Letters, Arts, and Sciences, University of Southern California, Los Angeles, CA
| | - Alan G Watts
- Center for NeuroMetabolic Interactions, The Integrated and Evolutionary Biology Graduate Program, and The Department of Biological Sciences, USC Dornsife College of Letters, Arts, and Sciences, University of Southern California, Los Angeles, CA
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19
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Abstract
It is now widely accepted that the brain makes important contributions to the dysregulated glucose metabolism, altered feeding behaviors, and the obesity often seen in type 2 diabetes (T2D). Although studies focusing on genetic, cellular, and molecular regulatory elements in pancreas, liver, adipose tissue etc provide a good understanding of how these processes relate to T2D, our knowledge of how brain wiring patterns are organized is much less developed. This article discusses animal studies that illustrate the importance of understanding the network organization of those brain regions most closely implicated in T2D. It will describe the brain networks, as well as the methodologies used to explore them. To illustrate some of the gaps in our knowledge, we will discuss the connectional network of the ventromedial nucleus and its adjacent cell groups in the hypothalamus; structures that are widely recognized as key elements in the brain's ability to control glycemia, feeding, and body weight.
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Affiliation(s)
- Alan G Watts
- The Center for NeuroMetabolic Interactions and The Department of Biological Sciences, USC Dornsife College of Letters, Arts, and Sciences, University of Southern California, Hedco Neuroscience Building, MC 2520, Los Angeles, CA, 90089-2520, USA,
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20
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Khan AM, Walker EM, Dominguez N, Watts AG. Neural input is critical for arcuate hypothalamic neurons to mount intracellular signaling responses to systemic insulin and deoxyglucose challenges in male rats: implications for communication within feeding and metabolic control networks. Endocrinology 2014; 155:405-16. [PMID: 24265445 PMCID: PMC3891932 DOI: 10.1210/en.2013-1480] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The hypothalamic arcuate nucleus (ARH) controls rat feeding behavior in part through peptidergic neurons projecting to the hypothalamic paraventricular nucleus (PVH). Hindbrain catecholaminergic (CA) neurons innervate both the PVH and ARH, and ablation of CA afferents to PVH neuroendocrine neurons prevents them from mounting cellular responses to systemic metabolic challenges such as insulin or 2-deoxy-d-glucose (2-DG). Here, we asked whether ablating CA afferents also limits their ARH responses to the same challenges or alters ARH connectivity with the PVH. We examined ARH neurons for three features: (1) CA afferents, visualized by dopamine-β-hydroxylase (DBH)- immunoreactivity; (2) activation by systemic metabolic challenge, as measured by increased numbers of neurons immunoreactive (ir) for phosphorylated ERK1/2 (pERK1/2); and (3) density of PVH-targeted axons immunoreactive for the feeding control peptides Agouti-related peptide and α-melanocyte-stimulating hormone (αMSH). Loss of PVH DBH immunoreactivity resulted in concomitant ARH reductions of DBH-ir and pERK1/2-ir neurons in the medial ARH, where AgRP neurons are enriched. In contrast, pERK1/2 immunoreactivity after systemic metabolic challenge was absent in αMSH-ir ARH neurons. Yet surprisingly, axonal αMSH immunoreactivity in the PVH was markedly increased in CA-ablated animals. These results indicate that (1) intrinsic ARH activity is insufficient to recruit pERK1/2-ir ARH neurons during systemic metabolic challenges (rather, hindbrain-originating CA neurons are required); and (2) rats may compensate for a loss of CA innervation to the ARH and PVH by increased expression of αMSH. These findings highlight the existence of a hierarchical dependence for ARH responses to neural and humoral signals that influence feeding behavior and metabolism.
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Affiliation(s)
- Arshad M Khan
- UTEP Systems Neuroscience Laboratory (A.M.K., E.M.W., N.D.), Border Biomedical Research Center (A.M.K., E.M.W.), Department of Biological Sciences (A.M.K., E.M.W., N.D.), and Graduate Program in Pathobiology (E.M.W.), University of Texas at El Paso, El Paso, Texas 79968; and Department of Biological Sciences (A.M.K., A.G.W.), University of Southern California, Los Angeles, Los Angeles, California 90089
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21
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Abstract
Blood glucose concentration is tightly regulated by the rate of insulin secretion and clearance, a process partially controlled by sensory neurons serving as metabolic sensors in relevant tissues. The activity of these neurons is regulated by the products of metabolism which regulate transmitter release, and recent evidence suggests that neuronally expressed ion channels of the transient receptor potential (TRP) family function in this critical process. Here, we report the novel finding that the cold and menthol-gated channel TRPM8 is necessary for proper insulin homeostasis. Mice lacking TRPM8 respond normally to a glucose challenge while exhibiting prolonged hypoglycemia in response to insulin. Additionally, Trpm8-/- mice have increased rates of insulin clearance compared with wild-type animals and increased expression of insulin-degrading enzyme in the liver. TRPM8 channels are not expressed in the liver, but TRPM8-expressing sensory afferents innervate the hepatic portal vein, suggesting a TRPM8-mediated neuronal control of liver insulin clearance. These results demonstrate that TRPM8 is a novel regulator of serum insulin and support the role of sensory innervation in metabolic homeostasis.
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Affiliation(s)
- Daniel D McCoy
- Neurobiology Section, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA
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22
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Kaminski KL, Watts AG. Intact catecholamine inputs to the forebrain are required for appropriate regulation of corticotrophin-releasing hormone and vasopressin gene expression by corticosterone in the rat paraventricular nucleus. J Neuroendocrinol 2012; 24:1517-26. [PMID: 22831701 PMCID: PMC3502639 DOI: 10.1111/j.1365-2826.2012.02363.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Revised: 07/06/2012] [Accepted: 07/19/2012] [Indexed: 02/04/2023]
Abstract
Corticotrophin-releasing hormone (CRH) neuroendocrine neurones in the paraventricular nucleus of the hypothalamus (PVH) drive adrenocorticotrophic hormone (ACTH) and thereby glucocorticoid release from pituitary corticotrophs and the adrenal cortex, respectively. Glucocorticoids suppress the ability of neuroendocrine corticotrophin-releasing hormone (CRH) neurones to synthesise and release ACTH secretogogues. Despite the importance of glucocorticoids as regulatory signals to CRH neurones in the extended time domain, how and where they act in this capacity is still not fully understood. Ascending catecholamine projections encode important cardiovascular, metabolic and other visceral information to the rat PVH and surrounding hypothalamus. These afferents have previously been implicated as targets for glucocorticoid action, including a role in the feedback regulation of PVH neuroendocrine neurones. To determine the contribution of these neurones to the long-term actions of corticosterone on CRH and vasopressin (AVP) gene expression in the PVH, we used an immunocytotoxin (a conjugate of the cytotoxin saporin and an antibody against dopamine-β-hydroxylase) that specifically ablates adrenergic and noradrenergic neurones. Lesions were administered to intact animals and to adrenalectomised animals with either no corticosterone or corticosterone replacement that provided levels above those required to normalise Crh expression. The ability of elevated levels of corticosterone to suppress Crh expression was abolished in animals lacking catecholaminergic innervation of the PVH. No effect was seen in the absence of corticosterone or in animals with intact adrenals. Furthermore, Avp expression, which is increased in CRH neurones following adrenalectomy, was suppressed in adrenalectomised catecholaminergic-lesioned animals. Interactions between corticosterone and catecholaminergic projections to the hypothalamus therefore make significant contributions to the regulation of Crh and Avp expression. However, the importance of catecholamine inputs is only apparent when circulating corticosterone concentrations are maintained either below or above those required to maintain the activity of the hypothalamic-pituitary-adrenal axis that is seen in intact animals.
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Affiliation(s)
- K L Kaminski
- The Neuroscience Graduate Program and Department of Biological Sciences, USC Dornsife College of Letters, Arts, and Sciences, University of Southern California, Los Angeles, CA 90089-2520, USA
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23
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Liu Y, Poon V, Sanchez-Watts G, Watts AG, Takemori H, Aguilera G. Salt-inducible kinase is involved in the regulation of corticotropin-releasing hormone transcription in hypothalamic neurons in rats. Endocrinology 2012; 153:223-33. [PMID: 22109884 PMCID: PMC3249682 DOI: 10.1210/en.2011-1404] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Activation of CRH transcription requires phosphorylation of cAMP response element-binding protein (CREB) and translocation of the CREB coactivator, transducer of regulated CREB activity (TORC) from cytoplasm to nucleus. In basal conditions, transcription is low because TORC remains in the cytoplasm, inactivated by phosphorylation through Ser/Thr protein kinases of the AMP-dependent protein kinases (AMPK) family, including salt-inducible kinase (SIK). To determine which kinase is responsible for TORC phosphorylation in CRH neurons, we measured SIK1 and SIK2 mRNA in the hypothalamic paraventricular nucleus of rats by in situ hybridization. In basal conditions, low mRNA levels of the two kinases were found in the dorsomedial paraventricular nucleus, consistent with location in CRH neurons. One hour of restraint stress increased SIK1 mRNA levels, whereas SIK2 mRNA showed only minor increases. In 4B hypothalamic neurons, or primary cultures, SIK1 mRNA (but not SIK2 mRNA) was inducible by the cAMP stimulator, forskolin. Overexpression of either SIK1 or SIK2 in 4B cells reduced nuclear TORC2 levels (Western blot) and inhibited forskolin-stimulated CRH transcription (luciferase assay). Conversely, the nonselective SIK inhibitor, staurosporine, increased nuclear TORC2 content and stimulated CRH transcription in 4Bcells and primary neuronal cultures (heteronuclear RNA). Unexpectedly, in 4B cells specific short hairpin RNA knockdown of endogenous SIK2 but not SIK1 induced nuclear translocation of TORC2 and CRH transcription, suggesting that SIK2 mediates TORC inactivation in basal conditions, whereas induction of SIK1 limits transcriptional activation. The study provides evidence that SIK represses CRH transcription by inactivating TORC, providing a potential mechanism for rapid on/off control of CRH transcription.
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Affiliation(s)
- Ying Liu
- Section on Endocrine Physiology, Developmental Endocrinology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, 10 Center Drive, Bethesda, Maryland 20892, USA
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Boyle CN, Lorenzen SM, Compton D, Watts AG. Dehydration-anorexia derives from a reduction in meal size, but not meal number. Physiol Behav 2011; 105:305-14. [PMID: 21854794 DOI: 10.1016/j.physbeh.2011.08.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2011] [Revised: 08/02/2011] [Accepted: 08/03/2011] [Indexed: 11/25/2022]
Abstract
The anorexia that results from extended periods of cellular dehydration is an important physiological adaptation that limits the intake of osmolytes from food and helps maintain the integrity of fluid compartments. The ability to experimentally control both the development and reversal of anorexia, together with the understanding of underlying hormonal and neuropeptidergic signals, makes dehydration (DE)-anorexia a powerful model for exploring the interactions of neural networks that stimulate and inhibit food intake. However, it is not known which meal parameters are affected by cellular dehydration to generate anorexia. Here we use continuous and high temporal resolution recording of food and fluid intake, together with a drinking-explicit method of meal pattern analysis to explore which meal parameters are modified during DE-anorexia. We find that the most important factor responsible for DE-anorexia is the failure to maintain feeding behavior once a meal has started, rather than the ability to initiate a meal, which remains virtually intact. This outcome is consistent with increased sensitivity to satiation signals and post-prandial satiety mechanisms. We also find that DE-anorexia significantly disrupts the temporal distribution of meals across the day so that the number of nocturnal meals gradually decreases while diurnal meal number increases. Surprisingly, once DE-anorexia is reversed this temporal redistribution is maintained for at least 4 days after normal food intake has resumed, which may allow increased daily food intake even after normal satiety mechanisms are reinstated. Therefore, DE-anorexia apparently develops from a selective targeting of those neural networks that control meal termination, whereas meal initiation mechanisms remain viable.
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Affiliation(s)
- Christina N Boyle
- The Neuroscience Graduate Program, University of Southern California, Los Angeles, CA 90089-2520, United States.
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Watts AG, Sanchez-Watts G, Liu Y, Aguilera G. The distribution of messenger RNAs encoding the three isoforms of the transducer of regulated cAMP responsive element binding protein activity in the rat forebrain. J Neuroendocrinol 2011; 23:754-66. [PMID: 21679259 PMCID: PMC3420016 DOI: 10.1111/j.1365-2826.2011.02178.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Increasing evidence indicates that the cAMP responsive element binding protein (CREB)-dependent transcriptional activation of a number of genes requires the CREB co-activator: transducer of regulated CREB activity (TORC). Because of the central importance of CREB in many brain functions, we examined the topographic distribution of TORC1, 2, and 3 mRNAs in specific regions of the rat forebrain. In situ hybridisation analysis revealed that TORC1 is the most abundant isoform in most forebrain structures, followed by TORC2 and TORC3. All three TORC isoforms were found in a number of brain nuclei, the ventricular ependyma and pia mater. Although high levels of TORC1 were widely distributed in the forebrain, TORC2 was found in discrete nuclei and TORC3 mostly in the ependyma, and pia mater. The relative expression of TORC isoforms was confirmed by quantitative reverse transcriptase-polymerase chain reaction analysis in the hippocampus and hypothalamus. In the paraventricular nucleus of the hypothalamus, TORC1 and 2 mRNAs were abundant in the parvicellular and magnocellular neuroendocrine compartments, whereas TORC3 expression was low. All three isoform mRNAs were found elsewhere in the hypothalamus, with the most prominent expression of TORC1 in the ventromedial nucleus, TORC2 in the dorsomedial and arcuate nuclei, TORCs 1 and 2 in the supraoptic nucleus, and TORC2 in the suprachiasmatic nucleus. These differential distribution patterns are consistent with complex roles for all three TORC isoforms in diverse brain structures, and provide a foundation for further studies on the mechanisms of CREB/TORC signalling on brain function.
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Affiliation(s)
- Alan G Watts
- Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089-2520, USA.
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Watts AG. Structure and function in the conceptual development of mammalian neuroendocrinology between 1920 and 1965. ACTA ACUST UNITED AC 2010; 66:174-204. [PMID: 20637232 DOI: 10.1016/j.brainresrev.2010.07.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2010] [Revised: 06/20/2010] [Accepted: 07/07/2010] [Indexed: 11/28/2022]
Abstract
With the growing realization in the 1930s that the brain played a crucial role in regulating the secretions of the pituitary gland, neuroendocrinology as we now know it developed from two rather separate directions. One approach relied heavily on morphological techniques to define neurosecretion; a novel, but for many years flawed model that was originally developed to explain the presence of gland-like cells in the diencephalon. During its first 20 years neurosecretion, as a concept, made no significant contribution to our understanding of how the pituitary was controlled. Then, following the identification by Sanford Palay and Wolfgang Bargmann of a continuous neurosecretory pathway from the hypothalamus to the neural lobe, neurosecretion became incorporated into a more broadly based concept of pituitary function, particularly regarding the neural lobe. The second approach integrated structural and functional methods to investigate neural regulation of the pituitary. This work eventually explained how the pituitary was controlled by the brain. It led directly to our understanding of the control of vasopressin and oxytocin release by neuroendocrine terminals in the neural lobe, the neurohumoral control of the pars distalis, and eventually to a detailed description of the neural networks that control pituitary function. As increasingly sophisticated morphological, neurophysiological, and eventually molecular biological techniques were applied to the problem, the original notion of the diencephalic gland and neurosecretion became unsustainable. The gland-nerve cells of the 1930s became the neurosecretory cells of the 1940s and 1950s, and then finally neuroendocrine neurons in the 1960s. From then on neuroendocrinology developed into the more unified discipline we know today. The chronology of these two approaches will be examined here using examples from research that occurred approximately between 1920 and 1965. The goal is not to give a comprehensive history of pituitary function or neuroendocrinology. Instead, the focus will be to compare the rationales and effectiveness of two contrasting experimental approaches: predominantly structural analyses as opposed to more integrated approaches.
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Affiliation(s)
- Alan G Watts
- Department of Biological Sciences, The USC College, University of Southern California, Los Angeles, CA 90089-2520, USA.
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Abstract
The anorexia that accompanies the drinking of hypertonic saline (DE-anorexia) is a critical adaptive behavioral mechanism that helps protect the integrity of fluid compartments during extended periods of cellular dehydration. Feeding is rapidly reinstated once drinking water is made available again. The relative simplicity and reproducibility of these behaviors makes DE-anorexia a very useful model for investigating how the various neural networks that control ingestive behaviors first suppress and then reinstate feeding. We show that DE-anorexia develops primarily because the mechanisms that terminate ongoing meals are upregulated in such a way as to significantly reduce meal size. At the same time however, signals generated by the ensuing negative energy balance appropriately activate neural mechanisms that can increase food intake. But as the output from these two competing processes is integrated, the net result is an increasing reduction of nocturnal food intake, despite the fact that spontaneous meals are initiated with the same frequency as in control animals. Furthermore, hypothalamic NPY injections also stimulate feeding in DE-anorexic animals with the same latency as controls, but again meals are prematurely terminated. Comparing Fos expression patterns across the brain following 2-deoxyglucose administration to control and DE-anorexic animals implicates neurons in the descending part of the parvicellular paraventricular nucleus of the hypothalamus and the lateral hypothalamic areas as key components of the networks that control DE-anorexia. Finally, DE-anorexia generates multiple inhibitory processes to suppress feeding. These are differentially disengaged once drinking water is reinstated. The paper represents an invited review by a symposium, award winner or keynote speaker at the Society for the Study of Ingestive Behavior [SSIB] Annual Meeting in Portland, July 2009.
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Affiliation(s)
- Alan G Watts
- The Center for NeuroMetabolic Interactions, The USC College, University of Southern California, Los Angeles, CA 90089-2520, United States.
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Abstract
Glucose is the primary fuel for the vast majority of cells, and animals have evolved essential cellular, autonomic, endocrine, and behavioral measures to counteract both hypo- and hyperglycemia. A central component of these counterregulatory mechanisms is the ability of specific sensory elements to detect changes in blood glucose and then use that information to produce appropriate counterregulatory responses. Here we focus on the organization of the neural systems that are engaged by glucosensing mechanisms when blood glucose concentrations fall to levels that pose a physiological threat. We employ a classic sensory-motor integrative schema to describe the peripheral, hindbrain, and hypothalamic components that make up counterregulatory mechanisms in the brain. We propose that models previously developed to describe how the forebrain modulates autonomic reflex loops in the hindbrain offer a reasoned framework for explaining how counterregulatory neural mechanisms in the hypothalamus and hindbrain are structured.
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Affiliation(s)
- Alan G Watts
- Center for NeuroMetabolic Interactions, USC College, University of Southern California, Los Angeles, CA 90089, USA.
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Salter-Venzon D, Watts AG. Site-specific attenuation of food intake but not the latency to eat after hypothalamic injections of neuropeptide Y in dehydrated-anorexic rats. Am J Physiol Regul Integr Comp Physiol 2009; 297:R1813-21. [PMID: 19741057 DOI: 10.1152/ajpregu.00116.2009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Anorexia that accompanies cellular dehydration in rats (DE-anorexia) offers a relatively simple model for investigating the functional organization of neural mechanisms that can suppress feeding during dehydration. Previous studies strongly suggest that the inputs that drive ingestive behavior control neurons in the paraventricular nucleus of the hypothalamus (PVH) and lateral hypothalamic area (LHA) remain active during DE-anorexia. Here we examine whether these two regions retain their sensitivity to neuropeptide Y (NPY). NPY is an important component in two major feeding-related inputs from the arcuate nucleus and the hindbrain. We found that intake responses to NPY injections in the LHA and PVH were suppressed in DE-anorexia, but the PVH remained less sensitive to the effects of NPY than the LHA in DE-anorexic animals. Indeed the higher dose of NPY (238 pmol) completely overcame shorter periods of DE-anorexia when injected into the LHA but not the PVH. However, the latency to eat after NPY injections remained unchanged from control animals, regardless of NPY dose, injection location, or intensity of anorexia. Furthermore, the onset and size of the strong and rapidly induced compensatory feeding that follows the return of water to DE-anorexic animals was also unaffected by any NPY injections. These data support the hypothesis that DE-anorexia develops as a consequence of the premature termination of regularly initiated meals, which perhaps involves processes that alter the sensitivity of satiety mechanisms downstream to the PVH and LHA.
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Affiliation(s)
- Dawna Salter-Venzon
- The Neuroscience Graduate Program and Department of Biological Sciences, University of Southern California College, University of Southern California, Los Angeles, California 90089-2520, USA
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Salter-Venzon D, Watts AG. The role of hypothalamic ingestive behavior controllers in generating dehydration anorexia: a Fos mapping study. Am J Physiol Regul Integr Comp Physiol 2008; 295:R1009-19. [PMID: 18667712 DOI: 10.1152/ajpregu.90425.2008] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Giving rats 2.5% saline to drink for 3-5 days simply and reliably generates anorexia. Despite having the neurochemical and hormonal markers of negative energy balance, dehydrated anorexic rats show a marked suppression of spontaneous food intake, as well as the feeding that is usually stimulated by overnight starvation or a 2-deoxy-d-glucose (2DG) challenge. These observations are consistent with a dehydration-dependent inhibition of the core circuitry that controls feeding. We hypothesize that this inhibition is directed at those neurons in the paraventricular nucleus and lateral hypothalamic area that constitute the hypothalamic "behavior controller" for feeding rather than their afferent inputs from the arcuate nucleus or hindbrain that convey critical feeding-related sensory information. To test this hypothesis, we mapped and quantified the Fos-immunoreactive response to 2DG in control and dehydrated rats drinking 2.5% saline. Our rationale was that regions showing an attenuated Fos response to 2DG in dehydrated animals would be strong candidates as the targets of dehydration-induced suppression of 2DG feeding. We found that the Fos response to combined dehydration and 2DG was attenuated only in the lateral hypothalamic area, with dehydration alone increasing Fos in the lateral part of the paraventricular nucleus. In the arcuate nucleus and those regions of the hindbrain that provide afferent inputs critical for the feeding response to 2DG, the Fos response to 2DG was unaffected by dehydration. Therefore, dehydration appears to target the lateral hypothalamic area and possibly the lateral part of the paraventricular nucleus to suppress the feeding response to 2DG.
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Affiliation(s)
- Dawna Salter-Venzon
- The Neuroscience Graduate Program and The Department of Biological Sciences, University of Southern California (USC) College, USC, Los Angeles, California 90089-2520, USA
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Gorton LM, Khan AM, Bohland M, Sanchez-Watts G, Donovan CM, Watts AG. A role for the forebrain in mediating time-of-day differences in glucocorticoid counterregulatory responses to hypoglycemia in rats. Endocrinology 2007; 148:6026-39. [PMID: 17823259 DOI: 10.1210/en.2007-0194] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The time of day influences the magnitude of ACTH and corticosterone responses to hypoglycemia. However, little is known about the mechanisms that impart these time-of-day differences on neuroendocrine CRH neurons in the hypothalamic paraventricular nucleus (PVH). Rats received 0-3 U/kg insulin (or 0.9% saline) to achieve a range of glucose nadir concentrations. Brains were processed to identify phosphorylated ERK1/2 (phospho-ERK1/2)-immunoreactive cells in the PVH and hindbrain and CRH heteronuclear RNA in the PVH. Hypoglycemia did not stimulate ACTH and corticosterone responses in animals unless a glucose concentration of approximately 3.15 mM or below was reached. Critically the glycemic thresholds required to stimulate ACTH and corticosterone release in the morning and night were indistinguishable. Yet glucose concentrations below the estimated glycemic threshold correlated with a greater increase in corticosterone, ACTH, and phospho-ERK1/2-immunoreactive neurons in the PVH at night, compared with morning. In these same animals, the number of phospho-ERK1/2-immunoreactive neurons in the medial part of the nucleus of the solitary tract was unchanged at both times of day. These data collectively support a model whereby changes in forebrain mechanisms alter the sensitivity of neuroendocrine CRH to the hypoglycemia-related information conveyed by ascending catecholaminergic afferents. Circadian clock-driven processes together with glucose-sensing elements in the forebrain would seem to be strong contenders for mediating these effects.
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Affiliation(s)
- Lori M Gorton
- The Neuroscience Research Institute, Hedco Neuroscience Building, University of Southern California, Los Angeles, CA 90089-2520, USA
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Khan AM, Ponzio TA, Sanchez-Watts G, Stanley BG, Hatton GI, Watts AG. Catecholaminergic control of mitogen-activated protein kinase signaling in paraventricular neuroendocrine neurons in vivo and in vitro: a proposed role during glycemic challenges. J Neurosci 2007; 27:7344-60. [PMID: 17611287 PMCID: PMC6794600 DOI: 10.1523/jneurosci.0873-07.2007] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Paraventricular hypothalamic (PVH) corticotropin-releasing hormone (CRH) neuroendocrine neurons mount neurosecretory and transcriptional responses to glycemic challenges [intravenous 2-deoxyglucose (2-DG) or insulin]. Although these responses require signals from intact afferents originating from hindbrain CA (catecholaminergic) neurons, the identity of these signals and the mechanisms by which they are transduced by PVH neurons during glycemic challenge remain unclear. Here, we tested whether the prototypical catecholamine, norepinephrine (NE), can reproduce PVH neuroendocrine responses to glycemic challenge. Because these responses include phosphorylation of p44/42 mitogen-activated protein (MAP) kinases [extracellular signal-regulated kinases 1/2 (ERK1/2)], we also determined whether NE activates ERK1/2 in PVH neurons and, if so, by what mechanism. We show that systemic insulin and 2-DG, and PVH-targeted NE microinjections, rapidly elevated PVH phospho-ERK1/2 levels. NE increased Crh and c-fos expression, together with circulating ACTH/corticosterone. However, because injections also increased c-Fos mRNA in other brain regions, we used hypothalamic slices maintained in vitro to clarify whether NE activates PVH neurons without contribution of inputs from distal regions. In slices, bath-applied NE triggered robust phospho-ERK1/2 immunoreactivity in PVH (including CRH) neurons, which attenuated markedly in the presence of the alpha1 adrenoceptor antagonist, prazosin, or the MAP kinase kinase (MEK) inhibitor, U0126 (1,4-diamino-2,3-dicyano-1,4-bis[2-aminophenylthio]butadiene). Therefore, at a systems level, local PVH delivery of NE is sufficient to account for hindbrain activation of CRH neuroendocrine neurons during glycemic challenge. At a cellular level, these data provide the first demonstration that MAP kinase signaling cascades (MEK-->ERK) are intracellular transducers of noradrenergic signals in CRH neurons, and implicate this transduction mechanism as an important component of central neuroendocrine responses during glycemic challenge.
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Affiliation(s)
- Arshad M Khan
- Neuroscience Research Institute and Department of Biological Sciences, University of Southern California, Los Angeles, California 90089-2520, USA.
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Watts AG, Sanchez-Watts G. Rapid and preferential activation of Fos protein in hypocretin/orexin neurons following the reversal of dehydration-anorexia. J Comp Neurol 2007; 502:768-82. [PMID: 17436292 DOI: 10.1002/cne.21316] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Dehydration (DE)-anorexia is stimulated by chronic consumption of hypertonic saline. Spontaneous nocturnal food intake is markedly reduced with this treatment but is rapidly reversed upon the return of drinking water. Here we examined the neurons in the lateral hypothalamic area (LHA) of chronically dehydrated rats for their peptidergic phenotype, colocalization, and activation profiles following the rapid reversal of anorexia. To do this, we used double-labeling combinations of Fos immunocytochemistry and radioisotopic- and digoxigenin-labeled in situ hybridization. We found that lateral hypothalamic corticotropin-releasing hormone (CRH) neurons show extensive coexpression with neurotensin mRNA, but they are distinct from hypocretin/orexin and melanin-concentrating hormone (MCH) neurons. Chronic dehydration increases Fos-ir in large numbers of neurons in dorsal regions of the LHA. Some of these LHA neurons also show increased CRH, but not hypocretin/orexin or MCH gene expression, as dehydration-anorexia develops. Furthermore, the behavioral sequence of eating and increased activity exhibited by DE animals in the minutes following water drinking is accompanied by a further increase in the number of Fos-ir nuclei in the LHA. Increased Fos activation occurs in a significant number of LHA hypocretin/orexin neurons, but not CRH or MCH neurons, in the LHA. Together these data implicate CRH but not hypocretin/orexin or MCH neurons in the LHA in the motor events associated with dehydration. However, when water is returned, contributions to the network controlling responses evidently come from hypocretin/orexin, but not CRH or MCH, neurons in the LHA.
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Affiliation(s)
- Alan G Watts
- The Neuroscience Research Institute and the Department of Biological Sciences, USC College, University of Southern California, Los Angeles, California 90089-2520, USA.
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Fujita S, Bohland M, Sanchez-Watts G, Watts AG, Donovan CM. Hypoglycemic detection at the portal vein is mediated by capsaicin-sensitive primary sensory neurons. Am J Physiol Endocrinol Metab 2007; 293:E96-E101. [PMID: 17374696 DOI: 10.1152/ajpendo.00415.2006] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To elucidate the type of spinal afferent involved in hypoglycemic detection at the portal vein, we considered the potential role of capsaicin-sensitive primary sensory neurons. Specifically, we examined the effect of capsaicin-induced ablation of portal vein afferents on the sympathoadrenal response to hypoglycemia. Under anesthesia, the portal vein was isolated in rats and either capsaicin (CAP) or the vehicle (CON) solution applied topically. During the same surgery, the carotid artery (sampling) and jugular vein (infusion) were cannulated. One week later, all animals underwent a hyperinsulinemic hypoglycemic clamp, with glucose (variable) and insulin (25 mU x kg(-1) x min(-1)) infused via the jugular vein. Systemic hypoglycemia (2.76 +/- 0.05 mM) was induced by minute 75 and sustained until minute 105. By design, no significant differences were observed in arterial glucose or insulin concentrations between groups. When hypoglycemia was induced in CON, the plasma epinephrine concentration increased from 0.67 +/- 0.05 nM at basal to 36.15 +/- 2.32 nM by minute 105. Compared with CON, CAP animals demonstrated an 80% suppression in epinephrine levels by minute 105, 7.11 +/- 0.55 nM (P < 0.001). A similar response to hypoglycemia was observed for norepinephrine, with CAP values suppressed by 48% compared with CON. Immunohistochemical analysis of the portal vein revealed an 85% decrease in the number of calcitonin gene-related peptide-reactive nerve fibers following capsaicin-induced ablation. That the suppression in the sympathoadrenal response was comparable to our previous findings for total denervation of the portal vein indicates that hypoglycemic detection at the portal vein is mediated by capsaicin-sensitive primary sensory neurons.
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Affiliation(s)
- Satoshi Fujita
- Department of Kinesiology, University of Southern California, Los Angeles, California 90089, USA
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Abstract
Many models have been proposed over the years to explain how motivated feeding behavior is controlled. One of the most compelling is based on the original concepts of Eliot Stellar whereby sets of interosensory and exterosensory inputs converge on a hypothalamic control network that can either stimulate or inhibit feeding. These inputs arise from information originating in the blood, the viscera, and the telencephalon. In this manner the relative strengths of the hypothalamic stimulatory and inhibitory networks at a particular time dictates how an animal feeds. Anorexia occurs when the balance within the networks consistently favors the restraint of feeding. This article discusses experimental evidence supporting a model whereby the increases in plasma osmolality that result from drinking hypertonic saline activate pathways projecting to neurons in the paraventricular nucleus of the hypothalamus (PVH) and lateral hypothalamic area (LHA). These neurons constitute the hypothalamic controller for ingestive behavior, and receive a set of afferent inputs from regions of the brain that process sensory information that is critical for different aspects of feeding. Important sets of inputs arise in the arcuate nucleus, the hindbrain, and in the telencephalon. Anorexia is generated in dehydrated animals by way of osmosensitive projections to the behavior control neurons in the PVH and LHA, rather than by actions on their afferent inputs.
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Affiliation(s)
- Alan G Watts
- The Neuroscience Research Institute and Neuroscience Graduate Program, USC College, University of Southern California, Los Angeles, CA 90089-2520, United States.
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Khan AM, Hahn JD, Cheng WC, Watts AG, Burns GAPC. NeuroScholar's electronic laboratory notebook and its application to neuroendocrinology. Neuroinformatics 2006; 4:139-62. [PMID: 16845166 PMCID: PMC4476904 DOI: 10.1385/ni:4:2:139] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/1999] [Revised: 11/30/1999] [Accepted: 11/30/1999] [Indexed: 11/11/2022]
Abstract
Scientists continually relate information from the published literature to their current research. The challenge of this essential and time-consuming activity increases as the body of scientific literature continues to grow. In an attempt to lessen the challenge, we have developed an Electronic Laboratory Notebook (ELN) application. Our ELN functions as a component of another application we have developed, an open-source knowledge management system for the neuroscientific literature called NeuroScholar (http://www. neuroscholar. org/). Scanned notebook pages, images, and data files are entered into the ELN, where they can be annotated, organized, and linked to similarly annotated excerpts from the published literature within Neuroscholar. Associations between these knowledge constructs are created within a dynamic node-and-edge user interface. To produce an interactive, adaptable knowledge base. We demonstrate the ELN's utility by using it to organize data and literature related to our studies of the neuroendocrine hypothalamic paraventricular nucleus (PVH). We also discuss how the ELN could be applied to model other neuroendocrine systems; as an example we look at the role of PVH stressor-responsive neurons in the context of their involvement in the suppression of reproductive function. We present this application to the community as open-source software and invite contributions to its development.
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Watts AG, Khan AM, Sanchez-Watts G, Salter D, Neuner CM. Activation in neural networks controlling ingestive behaviors: what does it mean, and how do we map and measure it? Physiol Behav 2006; 89:501-10. [PMID: 16828817 DOI: 10.1016/j.physbeh.2006.05.025] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2006] [Revised: 05/05/2006] [Accepted: 05/25/2006] [Indexed: 01/14/2023]
Abstract
Over the past thirty years many of different methods have been developed that use markers to track or image the activity of the neurons within the central networks that control ingestive behaviors. The ultimate goal of these experiments is to identify the location of neurons that participate in the response to an identified stimulus, and more widely to define the structure and function of the networks that control specific aspects of ingestive behavior. Some of these markers depend upon the rapid accumulation of proteins, while others reflect altered energy metabolism as neurons change their firing rates. These methods are widely used in behavioral neuroscience, but the way results are interpreted within the context of defining neural networks is constrained by how we answer the following questions. How well can the structure of the behavior be documented? What do we know about the processes that lead to the accumulation of the marker? What is the function of the marker within the neuron? How closely in time does the marker accumulation track the stimulus? How long does the marker persist after the stimulus is removed? We will review how these questions can be addressed with regard to ingestive and related behaviors. We will also discuss the importance of plotting the location of labeled cells using standardized atlases to facilitate the presentation and comparison of data between experiments and laboratories. Finally, we emphasize the importance of comprehensive and accurate mapping for using newly emerging technologies in neuroinfomatics.
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Affiliation(s)
- Alan G Watts
- Neuroscience Research Institute and Neuroscience Graduate Program, University of Southern California, Los Angeles, CA 90089-2520, United States.
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Swanson LW, Sanchez-Watts G, Watts AG. Comparison of melanin-concentrating hormone and hypocretin/orexin mRNA expression patterns in a new parceling scheme of the lateral hypothalamic zone. Neurosci Lett 2005; 387:80-4. [PMID: 16084021 DOI: 10.1016/j.neulet.2005.06.066] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2005] [Revised: 06/15/2005] [Accepted: 06/24/2005] [Indexed: 10/25/2022]
Abstract
A high-resolution spatial distribution analysis of hypothalamic neurons expressing melanin-concentrating hormone or hypocretin/orexin was performed in adult male rats with in situ hybridization cytochemistry. For the analysis, a new parcellation of the lateral zone with some two-dozen regions was used, and distributions were plotted on 15 transverse reference levels through the hypothalamus. Qualitatively the results confirm earlier, much lower resolution mapping studies, although some discrepancies are clarified. Previous work indicates that each of these cell populations is far from homogeneous, and the present results should help establish a framework for clarifying more precisely how they are differentiated and organized in terms of axonal input-output relationships and gene expression patterns, and for defining precise relationships with other hypothalamic neuron populations.
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Affiliation(s)
- Larry W Swanson
- Neuroscience Program, Department of Biological Sciences, University of Southern California, Hedco Neuroscience Building MC 2520, Room 428, 3641 Watt Way, Los Angeles, CA 90089-2520, USA.
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Watts AG. Glucocorticoid regulation of peptide genes in neuroendocrine CRH neurons: a complexity beyond negative feedback. Front Neuroendocrinol 2005; 26:109-30. [PMID: 16289311 DOI: 10.1016/j.yfrne.2005.09.001] [Citation(s) in RCA: 163] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/25/2005] [Accepted: 09/14/2005] [Indexed: 11/19/2022]
Abstract
This review will examine our current knowledge of a fundamental property of CRH neuroendocrine neurons: how the major endpoint of the HPA axis--adrenal glucocorticoids--interacts with the mechanisms controlling the expression of the genes that encode ACTH secretogogues. A great deal of work over the past 25 years has led to the notion that this question has an ostensibly simple answer: glucocorticoids inhibit peptide gene expression using "negative feedback" at the CRH neuron and elsewhere. However, closely examining how glucocorticoids act in different physiological circumstances reveals a much more complex set of answers, particularly if we consider how the processes that control peptide synthesis and release are coupled. Out of this examination emerges a more flexible and complex framework for examining the integrative mechanisms controlling the CRH neuron. Although we will mostly focus on the Crh gene, relevant aspects of the vasopressin (Avp) and pro-enkephalin (pEnk) gene regulatory mechanisms will also be discussed.
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Affiliation(s)
- Alan G Watts
- The Neuroscience Research Institute, and The Department of Biological Sciences, USC College, University of Southern California, Los Angeles, USA.
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Watts AG, Tanimura S, Sanchez-Watts G. Corticotropin-releasing hormone and arginine vasopressin gene transcription in the hypothalamic paraventricular nucleus of unstressed rats: daily rhythms and their interactions with corticosterone. Endocrinology 2004; 145:529-40. [PMID: 14563696 DOI: 10.1210/en.2003-0394] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
To drive the daily ACTH secretory rhythm from anterior pituitary corticotropes signals from the circadian clock schedule CRH and, to lesser extent, arginine vasopressin (AVP) release from neuroendocrine terminals. In turn, releasable pools of CRH and AVP in neuroendocrine terminals are sustained by synthetic mechanisms in the medial parvicellular paraventricular nucleus, a critical component of which involves transcribing primary (heteronuclear (hn)) RNA transcripts from their cognate genes. To determine the fundamental daily patterns of ACTH secretagogue gene transcription in unstressed rats, we measured CRH and AVP hnRNA levels at 1- to 4-h intervals throughout the day using in situ hybridization. Crh gene transcription is readily detectable throughout the day, and shows a pronounced rhythm that is temporally correlated with CRH mRNA levels, but is uncoupled from ACTH release. However, avp gene transcription is barely detectable and shows no discernable rhythm. We then performed similar experiments in adrenalectomized rats with or without corticosterone replacement. Corticosterone-dependent mechanisms regulate CRH hnRNA levels at the nadir and peak as well as the onset of nocturnal crh gene transcription. A prominent rhythm of avp hnRNA seen in adrenalectomized animals was dampened by corticosterone. This study shows, first, CRH synthesis in intact animals is maintained by a nocturnal episode of crh gene transcription, parameters of which are modulated by corticosterone-dependent mechanisms; second, circulating corticosterone is sufficient to completely inhibit a daily rhythm of avp gene transcription present in adrenalectomized rats; third, the neural systems that activate crh gene transcription can be uncoupled from those driving ACTH release.
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Affiliation(s)
- Alan G Watts
- Neuroscience Program and Department of Biological Sciences, University of Southern California, Hedco Neuroscience Building, mc 2520, 3641 Watt Way, Los Angeles, CA 90089-2520, USA.
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Khan AM, Watts AG. Intravenous 2-deoxy-D-glucose injection rapidly elevates levels of the phosphorylated forms of p44/42 mitogen-activated protein kinases (extracellularly regulated kinases 1/2) in rat hypothalamic parvicellular paraventricular neurons. Endocrinology 2004; 145:351-9. [PMID: 14525908 DOI: 10.1210/en.2003-0539] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
CRH neurons within the medial parvicellular part of the hypothalamic paraventricular nucleus (PVHmp) can respond to afferent inputs encoding stress-related information by initiating peptide synthesis (signaling cascades, transcription, and translation) and/or peptide release. However, understanding these cellular events is hampered by three outstanding issues: 1) neural inputs that activate CRH neurons remain incompletely identified; 2) the identity and temporal dynamics of signaling pathways within CRH neurons are poorly understood; and 3) the precise coupling of the first two issues has not been established. Here, we report that the phosphorylated forms of p44/p42 MAPKs (pERK1/2) are rapidly detected in PVHmp cells after i.v. infusion of the antimetabolite, 2-deoxy-D-glucose (2-DG). Combined immunocytochemistry and in situ hybridization revealed that pERK1/2 immunoreactivity is detectable 10 min after 2-DG infusion not only within most PVHmp neurons containing CRH mRNA (78.6% of mean total CRH cells counted) but also in many non-CRH neurons (45.5% of mean total sampled cells). In contrast, Fos protein in the PVHmp was not detected within this time period, consistent with the known time course for its translation. Stress associated with halothane exposure also robustly elevated pERK1/2 levels in PVHmp neurons approximately 10 min after exposure. Our results implicate pERK1/2 in stress-induced activation of CRH neurosecretory cells and underscore their utility as indices of rapid cellular activation. Because 2-DG-induced activation of CRH gene transcription in these neurons requires a catecholaminergic input, our data also suggest that pERK1/2 could couple afferent catecholaminergic signals with CRH gene expression in these neurons.
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Affiliation(s)
- Arshad M Khan
- Program in Neural, Informational and Behavioral Sciences, University of Southern California, Los Angeles, California 90089, USA.
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Ritter S, Watts AG, Dinh TT, Sanchez-Watts G, Pedrow C. Immunotoxin lesion of hypothalamically projecting norepinephrine and epinephrine neurons differentially affects circadian and stressor-stimulated corticosterone secretion. Endocrinology 2003; 144:1357-67. [PMID: 12639919 DOI: 10.1210/en.2002-221076] [Citation(s) in RCA: 122] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Hindbrain norepinephrine (NE) and epinephrine (E) neurons play a pivotal role in the central distribution of sensory signals derived from the internal environment. Their projections influence the various secretory patterns of the hypothalamo-pituitary-adrenal axis and are essential for feeding and adrenal medullary responses to glucoprivation. NE and E terminals in the paraventricular nucleus of the hypothalamus (PVH) and associated hindbrain cell bodies can be virtually eliminated by PVH microinjection of a retrogradely transported conjugate of saporin (SAP, a ribosomal toxin) and a monoclonal antibody against dopamine beta-hydroxylase (dbetah), i.e. dbetah mouse monoclonal antibody conjugated to SAP (DSAP). To examine the effects of selective elimination of NE/E afferents on hypothalamo-pituitary-adrenal activation, we injected DSAP into the PVH and measured corticosterone secretion under basal circadian conditions and in response to two distinct challenges: glucoprivation and forced swim. DSAP lesions profoundly impaired glucoprivation-induced corticosterone secretion and induction of CRH heteronuclear RNA and Fos mRNA in the PVH, without impairing basal CRH mRNA expression, circadian corticosterone release, or the corticosterone response to swim stress. Thus, NE/E projections influence corticosterone secretion only in certain circumstances. They are required for the response to glucoprivation, but are dispensable for circadian activation and for the response to swim stress.
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Affiliation(s)
- Sue Ritter
- Program in Neuroscience, Washington State University, Pullman, Washington 99164-6520, USA.
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Abstract
We have used the anorexia shown by rats given hypertonic saline to drink to investigate central mechanisms that can inhibit feeding. Rats dehydrated in this manner for 3 or 5 days showed a severe attenuation of the compensatory feeding observed after an overnight fast compared with control euhydrated rats or rats whose food was restricted to match the intake of anorexic rats. Food intake after injections of 2-deoxy-d-glucose (2-DG) was also significantly decreased in dehydrated animals compared with that after a 2-DG injection given before dehydration. However, all the dehydrated animals demonstrated a robust eating response after water was returned whether they had received injection of 2-DG or vehicle. Despite a profound reduction in 2-DG-induced feeding, other glucoregulatory responses to 2-DG remained intact in dehydrated animals. After 2-DG injection, corticosterone secretion and blood glucose were significantly elevated from preinjection values whether or not animals were dehydrated. Thus the mechanisms responsible for anorexia in dehydrated animals specifically target stimulatory feeding pathways but leave intact other counterregulatory glucometabolic motor events.
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Affiliation(s)
- Dawna Salter
- NIBS-Neuroscience Program and Department of Biological Sciences, University of Southern California, Los Angeles, California 90089-2520, USA
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Abstract
Drinking and eating are critically important motivated behaviors whose expression is usually tightly linked; under conditions of spontaneous intake, disruption of one usually disturbs the other. This characteristic is exemplified by dehydration-induced anorexia in which increasing plasma osmolality leads to a centrally generated reduction in food intake, which is then rapidly reversed as water is again made available. This review discusses, at a systems level, how the brain is organized to generate these behaviors and how dehydration affects the expression of neuropeptides in sets of anatomically defined forebrain circuits that contribute to the integration of motor outputs. These findings are then used to consider how altered neuropeptidergic signaling operates within motor drive networks and how these changes may impact the way neuroendocrine, autonomic, and behavioral motor systems respond to this fundamental homeostatic challenge.
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Affiliation(s)
- A G Watts
- The Neuroscience Program and the Department of Biological Sciences, University of Southern California, Los Angeles, California 90089-2520, USA.
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Dong HW, Petrovich GD, Watts AG, Swanson LW. Basic organization of projections from the oval and fusiform nuclei of the bed nuclei of the stria terminalis in adult rat brain. J Comp Neurol 2001; 436:430-55. [PMID: 11447588 DOI: 10.1002/cne.1079] [Citation(s) in RCA: 391] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The organization of axonal projections from the oval and fusiform nuclei of the bed nuclei of the stria terminalis (BST) was characterized with the Phaseolus vulgaris-leucoagglutinin (PHAL) anterograde tracing method in adult male rats. Within the BST, the oval nucleus (BSTov) projects very densely to the fusiform nucleus (BSTfu) and also innervates the caudal anterolateral area, anterodorsal area, rhomboid nucleus, and subcommissural zone. Outside the BST, its heaviest inputs are to the caudal substantia innominata and adjacent central amygdalar nucleus, retrorubral area, and lateral parabrachial nucleus. It generates moderate inputs to the caudal nucleus accumbens, parasubthalamic nucleus, and medial and ventrolateral divisions of the periaqueductal gray, and it sends a light input to the anterior parvicellular part of the hypothalamic paraventricular nucleus and nucleus of the solitary tract. The BSTfu displays a much more complex projection pattern. Within the BST, it densely innervates the anterodorsal area, dorsomedial nucleus, and caudal anterolateral area, and it moderately innervates the BSTov, subcommissural zone, and rhomboid nucleus. Outside the BST, the BSTfu provides dense inputs to the nucleus accumbens, caudal substantia innominata and central amygdalar nucleus, thalamic paraventricular nucleus, hypothalamic paraventricular and periventricular nuclei, hypothalamic dorsomedial nucleus, perifornical lateral hypothalamic area, and lateral tegmental nucleus. Moderately dense inputs are found in the parastrial, tuberal, dorsal raphé, and parabrachial nuclei and in the retrorubral area, ventrolateral division of the periaqueductal gray, and pontine central gray. Light projections end in the olfactory tubercle, lateral septal nucleus, posterior basolateral amygdalar nucleus, supramammillary nucleus, and nucleus of the solitary tract. These and other results suggest that the BSTov and BSTfu are basal telencephalic parts of a circuit that coordinates autonomic, neuroendocrine, and ingestive behavioral responses during stress.
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Affiliation(s)
- H W Dong
- Neuroscience Program, University of Southern California, Los Angeles, California 90089-2520, USA
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Abstract
This review will describe effects of corticosterone on the temporal dynamics of components within the hypothalamo-pituitary-adrenal (HPA) axis in response to sustained hypovolemia. The characterization of the synthetic and secretory profiles of HPA elements in these rat models reveals the complexities of steroid-mediated regulation of neuroendocrine and corticotrope function during a sustained stress event. Collectively, our data suggest activation of gene transcription and secretion are independently controlled, and that corticosterone affects adrenocorticotropin hormone (ACTH) gene expression in the parvicellular neuroendocrine part of the hypothalamic paraventricular nucleus using two mechanisms: first, an inhibition which contributes to classic negative feedback, and second, a facilitation, which is seen at low plasma concentrations.
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Affiliation(s)
- S M Tanimura
- Program in Neuroscience, The Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089-2520, USA
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Abstract
We have used in situ hybridization and radio-immunoassay to compare temporal dynamics of components in the hypothalamo-pituitary limb of the hypothalamo-pituitary-adrenal axis during sustained hypovolemic stress in adrenalectomized (ADX) rats to those previously reported in intact animals. We asked three questions: first, does corticotropin-releasing hormone (CRH) gene transcription occur in neuroendocrine neurones of the hypothalamic paraventricular nucleus (PVH) of ADX rats, and if so, how is it temporally organized; second, what is the expression pattern of the vasopressin and other genes known to be colocalized in these neuroendocrine neurones; third, if adrenocorticotropin hormone (ACTH) secretion occurs, what is its temporal profile? We found that sustained hypovolemia evoked a brief episode of CRH gene transcription in ADX rats that occurred earlier than in intact rats. However, in contrast to saline-injected controls, this activation was not maintained because declines in CRH hnRNA and mRNA were seen as the stress continued. Although increased vasopressin gene transcription was not seen in intact hypovolemic rats, robust increases were measured throughout in ADX rats, suggesting that in the absence of corticosterone the vasopressin gene is transcribed preferentially to the CRH gene during sustained hypovolemia. c-fos and preproenkephalin mRNA profiles also exhibited earlier onsets compared to intact rats. Finally, the onset and duration of ACTH secretion was the same in ADX rats as previously reported in intact rats. Collectively, these data support two hypotheses regarding the actions of corticosterone. First, that it provides some form of facilitatory signal allowing neuroendocrine CRH transcriptional mechanisms to remain active during sustained hypovolemia. Second, that it strongly inhibits the response of the vasopressin gene to hypovolemic stress.
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Affiliation(s)
- S M Tanimura
- Neuroscience Program, The Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089-2520, USA
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Abstract
Eating and drinking are motivated behaviors that are made up of coordinated sets of neuroendocrine, autonomic, and behavioral motor events. Although the spinal cord, hindbrain, and hypothalamus contain the motor neurons and circuitry sufficient to maintain the reflex parts of these motor events, inputs from the telencephalon are required to furnish the behavioral components with a motivated (goal-directed) character. Each of these motor events derives from the complex interaction of a variety of sensory inputs with groups of neural networks whose components are distributed throughout the brain and collectively support motor expression and coordination. At a first approximation based on a variety of data, these networks can be divided into three groups: networks that stimulate, those that inhibit, and those that disinhibit motor functions. A fourth contributor is the circadian timing signal that originates in the hypothalamic suprachiasmatic nucleus and provides the temporal anchor for the expression of all behaviors. This article discusses the nature of these networks using neuroanatomical (tract-tracing and neuropeptide in situ hybridization), endocrine, and behavioral evidence from a variety of experimental models. A persistent problem when studying the control of food intake from a neural systems perspective has been the difficulty in separating those neuronal changes that result in hunger from those that are as a consequence of eating. To address this problem, dehydration-associated anorexia is presented as a particularly useful experimental model because it can be used to distinguish between neural mechanisms underlying anorexia and those changes that occur as a consequence of anorexia. The article concludes by highlighting the potential role of neuropeptidergic action in the operation of these networks, using forebrain neuropeptidergic innervation of the parabrachial nucleus as an example.
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Affiliation(s)
- A G Watts
- The Neuroscience Program and the Department of Biological Sciences, University of Southern California, Los Angeles, California 90089-2520, USA.
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Watts AG, Sanchez-Watts G, Kelly AB. Distinct patterns of neuropeptide gene expression in the lateral hypothalamic area and arcuate nucleus are associated with dehydration-induced anorexia. J Neurosci 1999; 19:6111-21. [PMID: 10407047 PMCID: PMC6783090] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/1999] [Revised: 04/27/1999] [Accepted: 04/27/1999] [Indexed: 02/13/2023] Open
Abstract
We have investigated the hormonal and hypothalamic neuropeptidergic substrates of dehydration-associated anorexia. In situ hybridization and hormone analyses of anorexic and paired food-restricted rats revealed two distinct profiles. First, both groups had the characteristic gene expression and endocrine signatures usually associated with starvation: increased neuropeptide Y and decreased proopiomelanocortin and neurotensin mRNAs in the arcuate nucleus (ARH); increased circulating glucocorticoid but reduced leptin and insulin. Dehydrated animals are strongly anorexic despite these attributes, showing that the output of leptin- and insulin-sensitive ARH neurons that ordinarily stimulate eating must be inhibited. The second pattern occurred only in anorexic animals and had two components: (1) reduced corticotropin-releasing hormone (CRH) mRNA in the neuroendocrine paraventricular nucleus (PVH) and (2) increased CRH and neurotensin mRNAs in the lateral hypothalamic (LHA) and retrochiasmatic areas. However, neither corticosterone nor suppressed PVH CRH gene expression is required for anorexia after dehydration because PVH CRH mRNA in dehydrated adrenalectomized animals is unchanged from euhydrated adrenalectomized controls. We also showed that LHA CRH mRNA was strongly correlated with the intensity of anorexia, increased LHA CRH gene expression preceded the onset of anorexia, and dehydrated adrenalectomized animals (which also develop anorexia) had elevated LHA CRH gene expression with a distribution pattern similar to intact animals. Finally, we identified specific efferents from the CRH-containing region of the LHA to the PVH, thereby providing a neuroanatomical framework for the integration by the PVH of neuropeptidergic signals from the ARH and the LHA. Together, these observations suggest that CRH and neurotensin neurons in the LHA constitute a novel anatomical substrate for their well known anorexic effects.
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Affiliation(s)
- A G Watts
- The Neuroscience Program and the Department of Biological Sciences, University of Southern California, Los Angeles, California 90089-2520, USA
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Abstract
Corticotropin-releasing hormone immunoreactive (CRH-ir) neurons were examined in the hypothalamus of euhydrated and dehydrated rats without using colchicine. CRH-ir cells were observed in the lateral hypothalamus, retrochiasmatic, and in magnocellular parts of the supraoptic and paraventricular hypothalamic nucleus (PVH) in dehydrated but not euhydrated animals. However, CRH-ir neurons were decreased in the medial parvicellular part of the PVH. These results indicate that altered CRH mRNA levels previously reported in dehydrated animals translate into changes in peptide immunoreactivity.
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Affiliation(s)
- C Kay-Nishiyama
- Neuroscience Graduate Program and the Department of Biological Sciences, Hedco Neuroscience Building, MC 2520, University of Southern California, Los Angeles, CA 90089-2520, USA
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