1
|
Baumer-Harrison C, Breza JM, Sumners C, Krause EG, de Kloet AD. Sodium Intake and Disease: Another Relationship to Consider. Nutrients 2023; 15:535. [PMID: 36771242 PMCID: PMC9921152 DOI: 10.3390/nu15030535] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Revised: 01/14/2023] [Accepted: 01/15/2023] [Indexed: 01/22/2023] Open
Abstract
Sodium (Na+) is crucial for numerous homeostatic processes in the body and, consequentially, its levels are tightly regulated by multiple organ systems. Sodium is acquired from the diet, commonly in the form of NaCl (table salt), and substances that contain sodium taste salty and are innately palatable at concentrations that are advantageous to physiological homeostasis. The importance of sodium homeostasis is reflected by sodium appetite, an "all-hands-on-deck" response involving the brain, multiple peripheral organ systems, and endocrine factors, to increase sodium intake and replenish sodium levels in times of depletion. Visceral sensory information and endocrine signals are integrated by the brain to regulate sodium intake. Dysregulation of the systems involved can lead to sodium overconsumption, which numerous studies have considered causal for the development of diseases, such as hypertension. The purpose here is to consider the inverse-how disease impacts sodium intake, with a focus on stress-related and cardiometabolic diseases. Our proposition is that such diseases contribute to an increase in sodium intake, potentially eliciting a vicious cycle toward disease exacerbation. First, we describe the mechanism(s) that regulate each of these processes independently. Then, we highlight the points of overlap and integration of these processes. We propose that the analogous neural circuitry involved in regulating sodium intake and blood pressure, at least in part, underlies the reciprocal relationship between neural control of these functions. Finally, we conclude with a discussion on how stress-related and cardiometabolic diseases influence these circuitries to alter the consumption of sodium.
Collapse
Affiliation(s)
- Caitlin Baumer-Harrison
- Department of Physiology and Aging, College of Medicine, University of Florida, Gainesville, FL 32603, USA
- Center for Integrative Cardiovascular and Metabolic Disease, University of Florida, Gainesville, FL 32610, USA
- Center for Smell and Taste, University of Florida, Gainesville, FL 32610, USA
- Evelyn F. and William L. McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
| | - Joseph M. Breza
- Department of Psychology, College of Arts and Sciences, Eastern Michigan University, Ypsilanti, MI 48197, USA
| | - Colin Sumners
- Department of Physiology and Aging, College of Medicine, University of Florida, Gainesville, FL 32603, USA
- Center for Integrative Cardiovascular and Metabolic Disease, University of Florida, Gainesville, FL 32610, USA
- Evelyn F. and William L. McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
| | - Eric G. Krause
- Center for Integrative Cardiovascular and Metabolic Disease, University of Florida, Gainesville, FL 32610, USA
- Evelyn F. and William L. McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
- Department of Pharmacodynamics, College of Pharmacy, University of Florida, Gainesville, FL 32610, USA
| | - Annette D. de Kloet
- Department of Physiology and Aging, College of Medicine, University of Florida, Gainesville, FL 32603, USA
- Center for Integrative Cardiovascular and Metabolic Disease, University of Florida, Gainesville, FL 32610, USA
- Center for Smell and Taste, University of Florida, Gainesville, FL 32610, USA
- Evelyn F. and William L. McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
| |
Collapse
|
2
|
Santollo J, Daniels D, Leshem M, Schulkin J. Sex Differences in Salt Appetite: Perspectives from Animal Models and Human Studies. Nutrients 2023; 15:208. [PMID: 36615865 PMCID: PMC9824138 DOI: 10.3390/nu15010208] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 12/26/2022] [Accepted: 12/29/2022] [Indexed: 01/04/2023] Open
Abstract
Salt ingestion by animals and humans has been noted from prehistory. The search for salt is largely driven by a physiological need for sodium. There is a large body of literature on sodium intake in laboratory rats, but the vast majority of this work has used male rats. The limited work conducted in both male and female rats, however, reveals sex differences in sodium intake. Importantly, while humans ingest salt every day, with every meal and with many foods, we do not know how many of these findings from rodent studies can be generalized to men and women. This review provides a synthesis of the literature that examines sex differences in sodium intake and highlights open questions. Sodium serves many important physiological functions and is inextricably linked to the maintenance of body fluid homeostasis. Indeed, from a motivated behavior perspective, the drive to consume sodium has largely been studied in conjunction with the study of thirst. This review will describe the neuroendocrine controls of fluid balance, mechanisms underlying sex differences, sex differences in sodium intake, changes in sodium intake during pregnancy, and the possible neuronal mechanisms underlying these differences in behavior. Having reviewed the mechanisms that can only be studied in animal experiments, we address sex differences in human dietary sodium intake in reproduction, and with age.
Collapse
Affiliation(s)
- Jessica Santollo
- Department of Biology, University of Kentucky, Lexington, KY 40506, USA
| | - Derek Daniels
- Department of Biology, University at Buffalo, Buffalo, NY 14260, USA
| | - Micah Leshem
- School of Psychological Sciences, The University of Haifa, Haifa 3498838, Israel
| | - Jay Schulkin
- School of Medicine, University of Washington, Seattle, WA 98195, USA
| |
Collapse
|
3
|
Mathieu NM, Nakagawa P, Grobe CC, Reho JJ, Brozoski DT, Lu KT, Wackman KK, Ritter ML, Segar JL, Grobe JL, Sigmund CD. ARRB2 (β-Arrestin-2) Deficiency Alters Fluid Homeostasis and Blood Pressure Regulation. Hypertension 2022; 79:2480-2492. [PMID: 36215165 PMCID: PMC9669141 DOI: 10.1161/hypertensionaha.122.19863] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Accepted: 08/04/2022] [Indexed: 11/16/2022]
Abstract
BACKGROUND GPCRs (G protein-coupled receptors) are implicated in blood pressure (BP) and fluid intake regulation. There is a developing concept that these effects are mediated by both canonical G protein signaling and noncanonical β-arrestin mediated signaling, but the contributions of each remain largely unexplored. Here, we hypothesized that β-arrestin contributes to fluid homeostasis and blood pressure (BP) regulation in deoxycorticosterone acetate (DOCA) salt hypertension, a prototypical model of salt-sensitive hypertension. METHODS Global β-arrestin1 (Arrb1) and β-arrestin2 (Arrb2) knockout mice were employed to evaluate drinking behavior, and BP was evaluated in Arrb2-knockout mice. Age- and sex-matched C57BL/6 mice served as controls. We measured intake of water and different sodium chloride solutions and BP employing a 2-bottle choice paradigm with and without DOCA. RESULTS Without DOCA (baseline), Arrb2-knockout mice exhibited a significant elevation in saline intake with no change in water intake. With DOCA treatment, Arrb2-knockout mice exhibited a significant increase in both saline and water intake. Although Arrb2-knockout mice exhibited hypernatremia at baseline conditions, we did not find significant changes in total body sodium stores or sodium palatability. In a separate cohort, BP was measured via telemetry in Arrb2-knockout and C57BL/6 mice with and without DOCA. Arrb2-knockout did not exhibit significant differences in BP before DOCA treatment when provided water alone, or when provided a choice of water and saline. However, Arrb2-knockout exhibited an increased pressor response to DOCA-salt. CONCLUSIONS These findings suggest that in salt-sensitive hypertension, ARRB2, but not ARRB1 (β-arrestin 1), might counterbalance the canonical signaling of GPCRs.
Collapse
Affiliation(s)
- Natalia M Mathieu
- Department of Physiology, Cardiovascular Center (N.M.M., P.N., J.J.R., D.T.B., K.-T.L., K.K.W., M.L.R., J.L.S., J.L.G., C.D.S.), Medical College of Wisconsin, Milwaukee, WI
| | - Pablo Nakagawa
- Department of Physiology, Cardiovascular Center (N.M.M., P.N., J.J.R., D.T.B., K.-T.L., K.K.W., M.L.R., J.L.S., J.L.G., C.D.S.), Medical College of Wisconsin, Milwaukee, WI
- Cardiovascular Center (P.N., J.L.S., J.L.G., C.D.S.), Medical College of Wisconsin, Milwaukee, WI
| | - Connie C Grobe
- Department of Pediatrics (C.C.G., J.L.S.), Medical College of Wisconsin, Milwaukee, WI
| | - John J Reho
- Department of Physiology, Cardiovascular Center (N.M.M., P.N., J.J.R., D.T.B., K.-T.L., K.K.W., M.L.R., J.L.S., J.L.G., C.D.S.), Medical College of Wisconsin, Milwaukee, WI
- Comprehensive Rodent Metabolic Phenotyping Core (J.J.R., J.L.G.), Medical College of Wisconsin, Milwaukee, WI
| | - Daniel T Brozoski
- Department of Physiology, Cardiovascular Center (N.M.M., P.N., J.J.R., D.T.B., K.-T.L., K.K.W., M.L.R., J.L.S., J.L.G., C.D.S.), Medical College of Wisconsin, Milwaukee, WI
| | - Ko-Ting Lu
- Department of Physiology, Cardiovascular Center (N.M.M., P.N., J.J.R., D.T.B., K.-T.L., K.K.W., M.L.R., J.L.S., J.L.G., C.D.S.), Medical College of Wisconsin, Milwaukee, WI
| | - Kelsey K Wackman
- Department of Physiology, Cardiovascular Center (N.M.M., P.N., J.J.R., D.T.B., K.-T.L., K.K.W., M.L.R., J.L.S., J.L.G., C.D.S.), Medical College of Wisconsin, Milwaukee, WI
| | - McKenzie L Ritter
- Department of Physiology, Cardiovascular Center (N.M.M., P.N., J.J.R., D.T.B., K.-T.L., K.K.W., M.L.R., J.L.S., J.L.G., C.D.S.), Medical College of Wisconsin, Milwaukee, WI
| | - Jeffrey L Segar
- Department of Physiology, Cardiovascular Center (N.M.M., P.N., J.J.R., D.T.B., K.-T.L., K.K.W., M.L.R., J.L.S., J.L.G., C.D.S.), Medical College of Wisconsin, Milwaukee, WI
- Cardiovascular Center (P.N., J.L.S., J.L.G., C.D.S.), Medical College of Wisconsin, Milwaukee, WI
- Department of Pediatrics (C.C.G., J.L.S.), Medical College of Wisconsin, Milwaukee, WI
| | - Justin L Grobe
- Department of Physiology, Cardiovascular Center (N.M.M., P.N., J.J.R., D.T.B., K.-T.L., K.K.W., M.L.R., J.L.S., J.L.G., C.D.S.), Medical College of Wisconsin, Milwaukee, WI
- Cardiovascular Center (P.N., J.L.S., J.L.G., C.D.S.), Medical College of Wisconsin, Milwaukee, WI
- Comprehensive Rodent Metabolic Phenotyping Core (J.J.R., J.L.G.), Medical College of Wisconsin, Milwaukee, WI
- Department of Biomedical Engineering (J.L.G.), Medical College of Wisconsin, Milwaukee, WI
| | - Curt D Sigmund
- Department of Physiology, Cardiovascular Center (N.M.M., P.N., J.J.R., D.T.B., K.-T.L., K.K.W., M.L.R., J.L.S., J.L.G., C.D.S.), Medical College of Wisconsin, Milwaukee, WI
- Cardiovascular Center (P.N., J.L.S., J.L.G., C.D.S.), Medical College of Wisconsin, Milwaukee, WI
| |
Collapse
|
4
|
Nuñez P, Arguelles J, Perillan C. Sex-specific influence of maternal exposure to bisphenol A on sodium and fluid balance in response to dipsogenic challenges in rats. Appetite 2022; 176:106091. [DOI: 10.1016/j.appet.2022.106091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Revised: 05/06/2022] [Accepted: 05/18/2022] [Indexed: 11/30/2022]
|
5
|
Reho JJ, Nakagawa P, Mouradian GC, Grobe CC, Saravia FL, Burnett CML, Kwitek AE, Kirby JR, Segar JL, Hodges MR, Sigmund CD, Grobe JL. Methods for the Comprehensive in vivo Analysis of Energy Flux, Fluid Homeostasis, Blood Pressure, and Ventilatory Function in Rodents. Front Physiol 2022; 13:855054. [PMID: 35283781 PMCID: PMC8914175 DOI: 10.3389/fphys.2022.855054] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Accepted: 02/03/2022] [Indexed: 01/22/2023] Open
Abstract
Cardiovascular disease represents the leading cause of death in the United States, and metabolic diseases such as obesity represent the primary impediment to improving cardiovascular health. Rodent (mouse and rat) models are widely used to model cardiometabolic disease, and as a result, there is increasing interest in the development of accurate and precise methodologies with sufficiently high resolution to dissect mechanisms controlling cardiometabolic physiology in these small organisms. Further, there is great utility in the development of centralized core facilities furnished with high-throughput equipment configurations and staffed with professional content experts to guide investigators and ensure the rigor and reproducibility of experimental endeavors. Here, we outline the array of specialized equipment and approaches that are employed within the Comprehensive Rodent Metabolic Phenotyping Core (CRMPC) and our collaborating laboratories within the Departments of Physiology, Pediatrics, Microbiology & Immunology, and Biomedical Engineering at the Medical College of Wisconsin (MCW), for the detailed mechanistic dissection of cardiometabolic function in mice and rats. We highlight selected methods for the analysis of body composition and fluid compartmentalization, electrolyte accumulation and flux, energy accumulation and flux, physical activity, ingestive behaviors, ventilatory function, blood pressure, heart rate, autonomic function, and assessment and manipulation of the gut microbiota. Further, we include discussion of the advantages and disadvantages of these approaches for their use with rodent models, and considerations for experimental designs using these methods.
Collapse
Affiliation(s)
- John J. Reho
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, United States,Comprehensive Rodent Metabolic Phenotyping Core, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Pablo Nakagawa
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, United States,Cardiovascular Center, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Gary C. Mouradian
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, United States,Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Connie C. Grobe
- Department of Pediatrics, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Fatima L. Saravia
- Department of Microbiology and Immunology, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Colin M. L. Burnett
- Department of Internal Medicine, University of Iowa Hospitals & Clinics, Iowa City, IA, United States
| | - Anne E. Kwitek
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, United States,Cardiovascular Center, Medical College of Wisconsin, Milwaukee, WI, United States,Department of Biomedical Engineering, Medical College of Wisconsin, Milwaukee, WI, United States
| | - John R. Kirby
- Department of Microbiology and Immunology, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Jeffrey L. Segar
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, United States,Cardiovascular Center, Medical College of Wisconsin, Milwaukee, WI, United States,Department of Pediatrics, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Matthew R. Hodges
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, United States,Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Curt D. Sigmund
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, United States,Cardiovascular Center, Medical College of Wisconsin, Milwaukee, WI, United States,Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Justin L. Grobe
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, United States,Comprehensive Rodent Metabolic Phenotyping Core, Medical College of Wisconsin, Milwaukee, WI, United States,Cardiovascular Center, Medical College of Wisconsin, Milwaukee, WI, United States,Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, WI, United States,Department of Biomedical Engineering, Medical College of Wisconsin, Milwaukee, WI, United States,*Correspondence: Justin L. Grobe,
| |
Collapse
|
6
|
Sodium Imbalance in Mice Results Primarily in Compensatory Gene Regulatory Responses in Kidney and Colon, but Not in Taste Tissue. Nutrients 2020; 12:nu12040995. [PMID: 32260115 PMCID: PMC7230584 DOI: 10.3390/nu12040995] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Revised: 03/27/2020] [Accepted: 03/30/2020] [Indexed: 12/12/2022] Open
Abstract
Renal excretion and sodium appetite provide the basis for sodium homeostasis. In both the kidney and tongue, the epithelial sodium channel (ENaC) is involved in sodium uptake and sensing. The diuretic drug amiloride is known to block ENaC, producing a mild natriuresis. However, amiloride is further reported to induce salt appetite in rodents after prolonged exposure as well as bitter taste impressions in humans. To examine how dietary sodium content and amiloride impact on sodium appetite, mice were subjected to dietary salt and amiloride intervention and subsequently analyzed for ENaC expression and taste reactivity. We observed substantial changes of ENaC expression in the colon and kidney confirming the role of these tissues for sodium homeostasis, whereas effects on lingual ENaC expression and taste preferences were negligible. In comparison, prolonged exposure to amiloride-containing drinking water affected β- and αENaC expression in fungiform and posterior taste papillae, respectively, next to changes in salt taste. However, amiloride did not only change salt taste sensation but also perception of sucrose, glutamate, and citric acid, which might be explained by the fact that amiloride itself activates bitter taste receptors in mice. Accordingly, exposure to amiloride generally affects taste impression and should be evaluated with care.
Collapse
|
7
|
Abstract
That the perceptual world of human taste is made up of four or five basic taste qualities is commonly accepted in the field of taste perception. Nevertheless, critics identify two issues that challenge this view. First, some argue that the term "basic tastes" cannot be precisely defined and, thus, is scientifically meaningless. Others accept the concept of basic tastes but believe there are many more. I argue here that it is most parsimonious to employ a perceptual definition of basic taste. I conclude that there are indeed four basic tastes (with a potential fifth) that constitute the building blocks of the human taste experience. Evidence cited includes historical writings from Chinese, Indian, and Greek cultures, ethnopharmacological research, and modern biological and psychological investigations. These perceptual "data" provide strong and convincing evidence, collected over thousands of years and from many different cultures, that the human perceptual world consists of the same basic taste qualities.
Collapse
Affiliation(s)
- Gary K Beauchamp
- Monell Chemical Senses Center , 3500 Market Street , Philadelphia , Pennsylvania 19104 , United States
| |
Collapse
|
8
|
Abstract
The study of taste has been guided throughout much of its history by the conceptual framework of psychophysics, where the focus was on quantification of the subjective experience of the taste sensations. By the mid-20th century, data from physiologic studies had accumulated sufficiently to assemble a model for the function of receptors that must mediate the initial stimulus of tastant molecules in contact with the tongue. But the study of taste as a receptor-mediated event did not gain momentum until decades later when the actual receptor proteins and attendant signaling mechanisms were identified and localized to the highly specialized taste-responsive cells of the tongue. With those discoveries a new opportunity to examine taste as a function of receptor activity has come into focus. Pharmacology is the science designed specifically for the experimental interrogation and quantitative characterization of receptor function at all levels of inquiry from molecules to behavior. This review covers the history of some of the major concepts that have shaped thinking and experimental approaches to taste, the seminal discoveries that have led to elucidation of receptors for taste, and how applying principles of receptor pharmacology can enhance understanding of the mechanisms of taste physiology and perception.
Collapse
Affiliation(s)
- R Kyle Palmer
- Opertech Bio, Inc., Pennovation Center, Philadelphia, Pennsylvania
| |
Collapse
|
9
|
Schier LA, Spector AC. The Functional and Neurobiological Properties of Bad Taste. Physiol Rev 2019; 99:605-663. [PMID: 30475657 PMCID: PMC6442928 DOI: 10.1152/physrev.00044.2017] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Revised: 05/18/2018] [Accepted: 06/30/2018] [Indexed: 12/12/2022] Open
Abstract
The gustatory system serves as a critical line of defense against ingesting harmful substances. Technological advances have fostered the characterization of peripheral receptors and have created opportunities for more selective manipulations of the nervous system, yet the neurobiological mechanisms underlying taste-based avoidance and aversion remain poorly understood. One conceptual obstacle stems from a lack of recognition that taste signals subserve several behavioral and physiological functions which likely engage partially segregated neural circuits. Moreover, although the gustatory system evolved to respond expediently to broad classes of biologically relevant chemicals, innate repertoires are often not in register with the actual consequences of a food. The mammalian brain exhibits tremendous flexibility; responses to taste can be modified in a specific manner according to bodily needs and the learned consequences of ingestion. Therefore, experimental strategies that distinguish between the functional properties of various taste-guided behaviors and link them to specific neural circuits need to be applied. Given the close relationship between the gustatory and visceroceptive systems, a full reckoning of the neural architecture of bad taste requires an understanding of how these respective sensory signals are integrated in the brain.
Collapse
Affiliation(s)
- Lindsey A Schier
- Department of Biological Sciences, University of Southern California , Los Angeles, California ; and Department of Psychology and Program in Neuroscience, Florida State University , Tallahassee, Florida
| | - Alan C Spector
- Department of Biological Sciences, University of Southern California , Los Angeles, California ; and Department of Psychology and Program in Neuroscience, Florida State University , Tallahassee, Florida
| |
Collapse
|
10
|
St John SJ, McBrayer AM, Krauskopf EE. Sodium Carbonate is Saltier Than Sodium Chloride to Sodium-Depleted Rats. Chem Senses 2017; 42:647-653. [PMID: 28981821 DOI: 10.1093/chemse/bjx043] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
In a series of behavioral experiments in the 1960s, G.R. Morrison identified several unique features of the taste of Na2CO3 to rats; namely, it is 1) considerably more intense than NaCl at isomolar concentrations, 2) avoided at 10 times lower concentrations than NaCl to thirsty rats, 3) preferred at 10 times lower concentrations than NaCl in sodium-depleted rats. He also demonstrated its qualitatively similarity to NaCl. In Experiment 1, we confirmed and extended many of Morrison's observations. Rats were injected with furosemide on 3 occasions to stimulate a sodium appetite. After each depletion, rats were given a brief-access taste test in a lickometer presenting, in random order, water and 7 concentrations of salt. One test used NaCl (0.028-0.89 M, quarter log steps), another used Na2CO3, and the third used Na2CO3, but at a tenfold lower concentration range (0.0028-0.089 M). Rats licked NaCl in an inverted-U shaped concentration-response function peaking at 0.158-0.281 M. As Morrison's results predicted, rats licked Na2CO3 in nearly identical fashion, but at a tenfold lower concentration range (peak at 0.0158-0.028 M). In a second experiment, furosemide-treated rats were repeatedly tested with the lower Na2CO3 range but mixed in the epithelial sodium channel blocker amiloride at various concentrations (3-300 μM, half log steps). Amiloride reduced licking for Na2CO3 and shifted the peak response rightward up to about half a log unit. Thus, this "super-saltiness" of Na2CO3 to rats is at least partly amiloride-dependent.
Collapse
Affiliation(s)
| | - Anya M McBrayer
- Department of Psychology, Rollins College, Winter Park, FL, USA
| | | |
Collapse
|
11
|
Norgren R. Sodium Taste During Sodium Appetite. Chem Senses 2016; 42:91-92. [PMID: 27920027 DOI: 10.1093/chemse/bjw112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Sodium appetite appears to be an excellent model to study the neural mechanisms of motivation. In this issue of Chemical Senses, experiments by St John (2016) challenge 2 hypotheses for how a systemic sodium deficit guides an animal to find and ingest more Na ions in the environment. Both hypotheses deal with modifications of the sensory neural code produced by Na+ ions on the tongue. One envisions a change in the Na+ signal amplitude. A reduction could make the strong Na+ signals less aversive; an increase, weak signals more noticeable. The other hypothesis requires no changes in the identity or amplitude of the Na+ signal, but a shift in its hedonic tone toward sweetness or reward. The results of the 3 behavioral experiments render both explanations unlikely but fail to suggest alternatives.
Collapse
Affiliation(s)
- Ralph Norgren
- Department of Neural and Behavioral Science, College of Medicine, The Pennsylvania State University, Hershey, PA, USA
| |
Collapse
|