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Ritchie HE, Polson JW, Xia A, Webster W. Effect of vinpocetine on embryonic heart rate in vitro. Curr Res Toxicol 2023; 5:100125. [PMID: 37753450 PMCID: PMC10518341 DOI: 10.1016/j.crtox.2023.100125] [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] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Revised: 09/11/2023] [Accepted: 09/14/2023] [Indexed: 09/28/2023] Open
Abstract
Vinpocetine is a readily available nutritional supplement claimed to improve memory and weight loss. However, it blocks the Ikr current essential for cardiac action potential repolarisation and Ikr inhibition can cause "torsade de pointes" arrhythmias and sudden death. Moreover, Ikr blockers have exhibited teratogenic effects in reproductive toxicology studies, leading to increased birth defects and embryonic mortality. The FDA advises against vinpocetine use in pregnant and prospective mothers based on animal studies showing dose-dependent fetal mortality in rats and rabbits, and cardiovascular malformations in surviving fetuses. However, the mechanisms responsible for vinpocetine's fetal toxicity remain unclear. The present study used rat embryo culture to evaluate vinpocetine and its major metabolite, apovincaminic acid, on embryonic heart rate, a possible causative factor behind its adverse effects. Both compounds induced embryonic bradycardia in a concentration-dependent manner, with vinpocetine proving more potent. The minimum vinpocentine concentration to induce bradycardia was 100 nM, a level unlikely to be reached in humans following typical doses. Embryonic arrhythmias were also observed at the highest concentrations. These results suggest that the FDA's cautionary statement may generate undue anxiety, although re-evaluation of teratogenicity risk associated with vinpocetine should be revisited if a link to cardiac arrhythmias in adults is established.
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Affiliation(s)
- Helen Elizabeth Ritchie
- School of Medical Sciences, Faculty of Medicine and Health, The University of Sydney, NSW, Australia
| | - Jaimie W. Polson
- School of Medical Sciences, Faculty of Medicine and Health, The University of Sydney, NSW, Australia
| | - Andrea Xia
- School of Medical Sciences, Faculty of Medicine and Health, The University of Sydney, NSW, Australia
| | - William Webster
- School of Medical Sciences, Faculty of Medicine and Health, The University of Sydney, NSW, Australia
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2
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Davis EA, Wald HS, Suarez AN, Zubcevic J, Liu CM, Cortella AM, Kamitakahara AK, Polson JW, Arnold M, Grill HJ, de Lartigue G, Kanoski SE. Ghrelin Signaling Affects Feeding Behavior, Metabolism, and Memory through the Vagus Nerve. Curr Biol 2020; 30:4510-4518.e6. [PMID: 32946754 PMCID: PMC7674191 DOI: 10.1016/j.cub.2020.08.069] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Revised: 07/10/2020] [Accepted: 08/20/2020] [Indexed: 02/07/2023]
Abstract
Vagal afferent neuron (VAN) signaling sends information from the gut to the brain and is fundamental in the control of feeding behavior and metabolism [1]. Recent findings reveal that VAN signaling also plays a critical role in cognitive processes, including affective motivational behaviors and hippocampus (HPC)-dependent memory [2-5]. VANs, located in nodose ganglia, express receptors for various gut-derived peptide signals; however, the function of these receptors with regard to feeding behavior, metabolism, and memory control is poorly understood. We hypothesized that VAN-mediated processes are influenced by ghrelin, a stomach-derived orexigenic hormone, via communication to its receptor (GHSR) expressed on gut-innervating VANs. To examine this hypothesis, rats received nodose ganglia injections of an adeno-associated virus (AAV) expressing short hairpin RNAs targeting GHSR (or a control AAV) for RNAi-mediated VAN-specific GHSR knockdown. Results reveal that VAN GHSR knockdown induced various feeding and metabolic disturbances, including increased meal frequency, impaired glucose tolerance, delayed gastric emptying, and increased body weight compared to controls. Additionally, VAN-specific GHSR knockdown impaired HPC-dependent contextual episodic memory and reduced HPC brain-derived neurotrophic factor expression, but did not affect anxiety-like behavior or general activity levels. A functional role for endogenous VAN GHSR signaling was further confirmed by results revealing that VAN signaling is required for the hyperphagic effects of ghrelin administered at dark onset, and that gut-restricted ghrelin-induced increases in VAN firing rate require intact VAN GHSR expression. Collective results reveal that VAN GHSR signaling is required for both normal feeding and metabolic function as well as HPC-dependent memory.
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Affiliation(s)
- Elizabeth A Davis
- Department of Biological Sciences, Human and Evolutionary Biology Section, Dornsife College of Letters, Arts and Sciences, University of Southern California, Los Angeles, CA 90089, USA
| | - Hallie S Wald
- Institute of Diabetes, Obesity and Metabolism, Graduate Groups of Psychology and Neuroscience, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Andrea N Suarez
- Department of Biological Sciences, Human and Evolutionary Biology Section, Dornsife College of Letters, Arts and Sciences, University of Southern California, Los Angeles, CA 90089, USA
| | - Jasenka Zubcevic
- Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL 32610, USA
| | - Clarissa M Liu
- Neuroscience Graduate Program, University of Southern California, Los Angeles, CA, USA
| | - Alyssa M Cortella
- Department of Biological Sciences, Human and Evolutionary Biology Section, Dornsife College of Letters, Arts and Sciences, University of Southern California, Los Angeles, CA 90089, USA
| | | | - Jaimie W Polson
- School of Medical Sciences & Bosch Institute, The University of Sydney, Sydney 2006, Australia
| | - Myrtha Arnold
- Department of Health Sciences and Technology, ETH Zurich, Zurich 8092, Switzerland
| | - Harvey J Grill
- Institute of Diabetes, Obesity and Metabolism, Graduate Groups of Psychology and Neuroscience, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Guillaume de Lartigue
- Pharmacodynamics Department, College of Pharmacy, University of Florida, Gainesville, FL 32610, USA; Center for Integrative Cardiovascular and Metabolic Disease, University of Florida, Gainesville, FL 32610, USA.
| | - Scott E Kanoski
- Department of Biological Sciences, Human and Evolutionary Biology Section, Dornsife College of Letters, Arts and Sciences, University of Southern California, Los Angeles, CA 90089, USA; Neuroscience Graduate Program, University of Southern California, Los Angeles, CA, USA.
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3
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Dissanayake HU, Anderson L, McMullan RL, Caterson ID, Hyett JA, Phang M, Raynes-Greenow C, Polson JW, Skilton MR, Gordon A. Influence of maternal and placental factors on newborn body composition. J Paediatr Child Health 2020; 56:224-230. [PMID: 31392795 DOI: 10.1111/jpc.14565] [Citation(s) in RCA: 3] [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] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Revised: 01/10/2019] [Accepted: 07/03/2019] [Indexed: 11/27/2022]
Abstract
AIM The objective of this study was to assess whether maternal characteristics, placental size or histological chorioamnionitis was associated with newborn body composition. Furthermore, we sought to determine whether placental weight may mediate the association between maternal pre-pregnancy weight and age with newborn body composition. METHODS A cross-sectional study was conducted at Royal Prince Alfred Hospital, Sydney, Australia. This study included 136 healthy, singleton, term-born newborns. Recruitment was stratified by newborn body fat percentiles (gender and gestational adjusted). Body fat was assessed by air displacement plethysmography. Placental examination was conducted by an anatomical pathologist. Maternal (chorioamnionitis) and fetal (chorionic and umbilical vasculitis, funisitis) inflammatory responses were classified according to Redline criteria. RESULTS Maternal pre-pregnancy weight, parity, labour, placental weight and surface area were associated with newborn fat mass and fat-free mass. Gestational diabetes and maternal age were associated with newborn fat mass but not fat-free mass. There was no association between histological chorioamnionitis and newborn body composition; however, spontaneous onset of labour was strongly associated with the presence of histological chorioamnionitis. Only 25-31% of the association of maternal weight and age with newborn fat mass was mediated via the placenta. CONCLUSIONS Maternal factors associated with newborn fat mass and fat-free mass differed, indicating that different mechanisms control fat mass and fat-free mass. Our mediation analysis suggests that placental weight partly mediates the association of maternal factors with newborn body composition. Histological chorioamnionitis was not associated with newborn body composition.
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Affiliation(s)
- Hasthi U Dissanayake
- Boden Institute of Obesity, Nutrition, Exercise and Eating Disorders, The University of Sydney, Sydney, New South Wales, Australia.,Sydney Medical School, D17 - Charles Perkins Centre, The University of Sydney, Sydney, New South Wales, Australia
| | - Lyndal Anderson
- Sydney Medical School, D17 - Charles Perkins Centre, The University of Sydney, Sydney, New South Wales, Australia.,Tissue Pathology, Royal Prince Alfred Hospital, Sydney, New South Wales, Australia
| | - Rowena L McMullan
- Boden Institute of Obesity, Nutrition, Exercise and Eating Disorders, The University of Sydney, Sydney, New South Wales, Australia.,Sydney Medical School, D17 - Charles Perkins Centre, The University of Sydney, Sydney, New South Wales, Australia.,Newborn Care, Royal Prince Alfred Hospital, Sydney, New South Wales, Australia
| | - Ian D Caterson
- Boden Institute of Obesity, Nutrition, Exercise and Eating Disorders, The University of Sydney, Sydney, New South Wales, Australia
| | - Jon A Hyett
- Sydney Medical School, D17 - Charles Perkins Centre, The University of Sydney, Sydney, New South Wales, Australia.,Women and Babies, Royal Prince Alfred Hospital, Sydney, New South Wales, Australia
| | - Melinda Phang
- Boden Institute of Obesity, Nutrition, Exercise and Eating Disorders, The University of Sydney, Sydney, New South Wales, Australia
| | | | - Jaimie W Polson
- School of Medical Sciences, University of Sydney, Sydney, New South Wales, Australia
| | - Michael R Skilton
- Boden Institute of Obesity, Nutrition, Exercise and Eating Disorders, The University of Sydney, Sydney, New South Wales, Australia.,Sydney Medical School, D17 - Charles Perkins Centre, The University of Sydney, Sydney, New South Wales, Australia
| | - Adrienne Gordon
- Sydney Medical School, D17 - Charles Perkins Centre, The University of Sydney, Sydney, New South Wales, Australia.,Newborn Care, Royal Prince Alfred Hospital, Sydney, New South Wales, Australia
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Dissanayake HU, McMullan RL, Gordon A, Caterson ID, Celermajer DS, Phang M, Raynes-Greenow C, Skilton MR, Polson JW. Noninvasive assessment of autonomic function in human neonates born at the extremes of fetal growth spectrum. Physiol Rep 2019; 6:e13682. [PMID: 29687617 PMCID: PMC5913591 DOI: 10.14814/phy2.13682] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Accepted: 03/22/2018] [Indexed: 01/23/2023] Open
Abstract
Birth weight is associated with adult cardiovascular disease, such that those at both ends of the spectrum are at increased risk. This may be driven in part by modification to autonomic control, a mechanistic contributor to hypertension. However, birth weight is a relatively crude surrogate of fetal growth; and newborn body composition may more accurately identify the "at risk" infant. Accordingly, we sought to determine whether newborns with high or low body fat have altered autonomic control of vasomotor function and cardiac contractility. Body fat was assessed by air-displacement plethysmography <24 h postnatal. Measures of spontaneous baroreflex sensitivity (sBRS), blood pressure variability (BPV), and dP/dtmax variability were compared between newborns categorized according to established body fat percentiles: high body fat (HBF, >90th percentile, n = 7), low body fat (LBF, ≤10th percentile, n = 12), and normal body fat (control, >25th to ≤75th percentile, n = 23). BPV was similar across body fat percentiles; similarly, low frequency dP/dtmax variability was similar across body fat percentiles. sBRS was reduced in HBF compared to controls (11.0 ± 6.0 vs. 20.1 ± 9.4 msec/mmHg, P = 0.03), but LBF did not differ (18.4 ± 6.0 msec/mmHg, P = 0.80). Across the entire body fat spectrum (n = 62), there was a nonlinear association between newborn body fat and sBRS (P = 0.03) that was independent of birth weight (P = 0.04). Autonomic modulation of vasomotor function and cardiac contractility in the newborn did not differ by body fat, but newborns born with high body fat show depressed baroreflex sensitivity.
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Affiliation(s)
- Hasthi U Dissanayake
- Boden Institute of Obesity, Nutrition, Exercise & Eating Disorders, The University of Sydney, Sydney, New South Wales, Australia.,Sydney Medical School, D17- Charles Perkins Centre, The University of Sydney, Sydney, New South Wales, Australia
| | - Rowena L McMullan
- Boden Institute of Obesity, Nutrition, Exercise & Eating Disorders, The University of Sydney, Sydney, New South Wales, Australia.,Sydney Medical School, D17- Charles Perkins Centre, The University of Sydney, Sydney, New South Wales, Australia.,Royal Prince Alfred Hospital, Sydney, New South Wales, Australia
| | - Adrienne Gordon
- Sydney Medical School, D17- Charles Perkins Centre, The University of Sydney, Sydney, New South Wales, Australia.,Royal Prince Alfred Hospital, Sydney, New South Wales, Australia
| | - Ian D Caterson
- Boden Institute of Obesity, Nutrition, Exercise & Eating Disorders, The University of Sydney, Sydney, New South Wales, Australia
| | - David S Celermajer
- Sydney Medical School, D17- Charles Perkins Centre, The University of Sydney, Sydney, New South Wales, Australia.,Royal Prince Alfred Hospital, Sydney, New South Wales, Australia
| | - Melinda Phang
- Boden Institute of Obesity, Nutrition, Exercise & Eating Disorders, The University of Sydney, Sydney, New South Wales, Australia
| | - Camille Raynes-Greenow
- Sydney School of Public Health, The University of Sydney, Sydney, New South Wales, Australia
| | - Michael R Skilton
- Boden Institute of Obesity, Nutrition, Exercise & Eating Disorders, The University of Sydney, Sydney, New South Wales, Australia.,Sydney Medical School, D17- Charles Perkins Centre, The University of Sydney, Sydney, New South Wales, Australia
| | - Jaimie W Polson
- School of Medical Sciences & Bosch Institute, The University of Sydney, Sydney, New South Wales, Australia
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Dissanayake HU, McMullan RL, Kong Y, Caterson ID, Celermajer DS, Phang M, Raynes-Greenow C, Polson JW, Gordon A, Skilton MR. Body Fatness and Cardiovascular Health in Newborn Infants. J Clin Med 2018; 7:jcm7090270. [PMID: 30208579 PMCID: PMC6162858 DOI: 10.3390/jcm7090270] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Revised: 09/04/2018] [Accepted: 09/08/2018] [Indexed: 11/16/2022] Open
Abstract
Birth weight is associated with cardiovascular disease, with those at both ends of the spectrum at increased risk. However, birth weight is a crude surrogate of fetal growth. Measures of body composition may more accurately identify high risk infants. We aimed to determine whether aortic wall thickening, cardiac autonomic control, and cardiac structure/function differ in newborns with high or low body fatness compared to those with average body fatness. 189 healthy singleton term born neonates were recruited and stratified by body fat percentiles (sex and gestation-specific). Infants with low body fat had higher aortic intima-media thickness (43 µm (95% confidence interval (CI) 7, 78), p = 0.02), lower heart rate variability (log total power, -0.5 (95% CI -0.8, -0.1), p = 0.008), and thicker ventricular walls (posterior wall thickness, 3.1 mm (95% CI 1.6, 4.6), p < 0.001) compared to infants with average body fatness. Infants with high body fat showed no differences in aortic intima-media thickness (-2 µm (95% CI -37, 33), p = 0.91) or cardiac structure compared to average body fatness, although stroke volume (-0.3 mL/kg (95% CI -0.6, -0.0), p = 0.003) and heart rate variability were lower (log total power, -0.8 (95% CI -1.1, -0.5), p < 0.001). The non-linear association of body fatness with heart rate variability was independent of birth weight. Infants born with low or high body fat have altered markers of cardiovascular health. Assessment of body fatness alongside birth weight may assist in identifying high risk individuals.
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Affiliation(s)
- Hasthi U Dissanayake
- Boden Institute of Obesity, Charles Perkins Centre, University of Sydney, Sydney, NSW 2006, Australia.
- Faculty of Medicine and Health, Charles Perkins Centre, The University of Sydney, Sydney, NSW 2006, Australia.
| | - Rowena L McMullan
- Boden Institute of Obesity, Charles Perkins Centre, University of Sydney, Sydney, NSW 2006, Australia.
- Faculty of Medicine and Health, Charles Perkins Centre, The University of Sydney, Sydney, NSW 2006, Australia.
- Royal Prince Alfred Hospital, Missenden Road, Camperdown, NSW 2050, Australia.
| | - Yang Kong
- Boden Institute of Obesity, Charles Perkins Centre, University of Sydney, Sydney, NSW 2006, Australia.
- Faculty of Medicine and Health, Charles Perkins Centre, The University of Sydney, Sydney, NSW 2006, Australia.
| | - Ian D Caterson
- Boden Institute of Obesity, Charles Perkins Centre, University of Sydney, Sydney, NSW 2006, Australia.
| | - David S Celermajer
- Faculty of Medicine and Health, Charles Perkins Centre, The University of Sydney, Sydney, NSW 2006, Australia.
- Royal Prince Alfred Hospital, Missenden Road, Camperdown, NSW 2050, Australia.
| | - Melinda Phang
- Boden Institute of Obesity, Charles Perkins Centre, University of Sydney, Sydney, NSW 2006, Australia.
| | | | - Jaimie W Polson
- Faculty of Medicine and Health, Charles Perkins Centre, The University of Sydney, Sydney, NSW 2006, Australia.
- School of Medical Sciences & Bosch Institute, The University of Sydney, Sydney, NSW 2006, Australia.
| | - Adrienne Gordon
- Faculty of Medicine and Health, Charles Perkins Centre, The University of Sydney, Sydney, NSW 2006, Australia.
- Royal Prince Alfred Hospital, Missenden Road, Camperdown, NSW 2050, Australia.
| | - Michael R Skilton
- Boden Institute of Obesity, Charles Perkins Centre, University of Sydney, Sydney, NSW 2006, Australia.
- Faculty of Medicine and Health, Charles Perkins Centre, The University of Sydney, Sydney, NSW 2006, Australia.
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6
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Ritchie HE, Oakes DJ, Kennedy D, Polson JW. Early Gestational Hypoxia and Adverse Developmental Outcomes. Birth Defects Res 2018; 109:1358-1376. [PMID: 29105381 DOI: 10.1002/bdr2.1136] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Accepted: 09/01/2017] [Indexed: 12/14/2022]
Abstract
Hypoxia is a normal and essential part of embryonic development. However, this state may leave the embryo vulnerable to damage when oxygen supply is disturbed. Embryofetal response to hypoxia is dependent on duration and depth of hypoxia, as well as developmental stage. Early postimplantation rat embryos were resilient to hypoxia, with many surviving up to 1.5 hr of uterine clamping, while most mid-gestation embryos were dead after 1 hour of clamping. Survivors were small and many had a range of defects, principally terminal transverse limb reduction defects. Similar patterns of malformations occurred when embryonic hypoxia was induced by maternal hypoxia, interruption of uteroplacental flow, or perfusion and embryonic bradycardia. There is good evidence that high altitude pregnancies are associated with smaller babies and increased risk of some malformations, but these results are complicated by increased risk of pre-eclampsia. Early onset pre-eclampsia itself is associated with small for dates and increased risk of atrio-ventricular septal defects. Limb defects have clearly been associated with chorionic villus sampling, cocaine, and misoprostol use. Similar defects are also observed with increased frequency among fetuses who are homozygous for thalassemia. Drugs that block the potassium current, whether as the prime site of action or as a side effect, are highly teratogenic in experimental animals. They induce embryonic bradycardia, hypoxia, hemorrhage, and blisters, leading to transverse limb defects as well as craniofacial and cardiovascular defects. While evidence linking these drugs to birth defects in humans is not compelling, the reason may methodological rather than biological. Birth Defects Research 109:1358-1376, 2017.© 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Helen E Ritchie
- Discipline of Biomedical Science, Sydney Medical School, University of Sydney, Sydney, NSW
| | - Diana J Oakes
- Discipline of Biomedical Science, Sydney Medical School, University of Sydney, Sydney, NSW
| | | | - Jaimie W Polson
- Discipline of Biomedical Science, Sydney Medical School, University of Sydney, Sydney, NSW
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Polson JW, Jayaratne SK. Tempol Prevents Hypertension in Maternal High Fat‐High Sucrose Diet Programmed Rats. FASEB J 2018. [DOI: 10.1096/fasebj.2018.32.1_supplement.lb314] [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: 11/11/2022]
Affiliation(s)
- Jaimie W Polson
- School of Medical ScienceUniversity of SydneyLidcombeAustralia
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Prestipino L, Polson JW, Brolin E, Ritchie HE. Long-term programming effects on blood pressure following gestational exposure to the I Kr blocker Dofetilide. Physiol Rep 2018; 6:e13621. [PMID: 29504284 PMCID: PMC5835481 DOI: 10.14814/phy2.13621] [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] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Revised: 01/02/2018] [Accepted: 01/03/2018] [Indexed: 11/24/2022] Open
Abstract
A slow embryonic heart rate in early-mid gestation is associated with increased risk of embryonic death and malformation, however, the long-term consequences remain unknown. We administered Dofetilide (Dof, 2.5 mg/kg), a drug that produces embryo-specific bradycardia, to pregnant rats from gestational days 11-14. Embryonic heart rate and rhythm were determined using embryo culture. Cardiovascular function was assessed in surviving adult offspring at rest, during acute psychological stress (air jet stress, AJS), and after 7 days of repeated AJS. Dof reduced embryonic HR by 40% for ~8 h on each of the treatment days. On postnatal day 3, Dof offspring were ~10% smaller. Blood pressure was elevated in adult Dof rats (systolic blood pressure, night: 103.8 ± 3.9 vs. 111.2 ± 3.0 mmHg, P = 0.01). While the pressor response to AJS was similar in both groups (control 17.7 ± 3.4; Dof 18.9 ± 0.9 mmHg, P = 0.74), after 7 days repeated AJS, clear habituation was present in control (P = 0.0001) but not Dof offspring (P = 0.48). Only Dof offspring showed a small increase in resting blood pressure after 7 days repeated stress (+3.9 ± 1.7 mmHg, P = 0.05). The results indicate that embryonic bradycardia programs hypertension and impaired stress adaptation, and have implications for the maternal use of cardioactive drugs during pregnancy.
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Affiliation(s)
- Louise Prestipino
- School of Medical Sciences and Bosch InstituteSydney Medical SchoolThe University of SydneySydneyNSWAustralia
| | - Jaimie W. Polson
- School of Medical Sciences and Bosch InstituteSydney Medical SchoolThe University of SydneySydneyNSWAustralia
| | - Elisabeth Brolin
- School of Medical Sciences and Bosch InstituteSydney Medical SchoolThe University of SydneySydneyNSWAustralia
| | - Helen E. Ritchie
- School of Medical Sciences and Bosch InstituteSydney Medical SchoolThe University of SydneySydneyNSWAustralia
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9
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Mckenzie KM, Dissanayake HU, McMullan R, Caterson ID, Celermajer DS, Gordon A, Hyett J, Meroni A, Phang M, Raynes-Greenow C, Polson JW, Skilton MR. Quantity and Quality of Carbohydrate Intake during Pregnancy, Newborn Body Fatness and Cardiac Autonomic Control: Conferred Cardiovascular Risk? Nutrients 2017; 9:nu9121375. [PMID: 29257088 PMCID: PMC5748825 DOI: 10.3390/nu9121375] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Revised: 12/12/2017] [Accepted: 12/12/2017] [Indexed: 12/20/2022] Open
Abstract
The fetal environment has an important influence on health and disease over the life course. Maternal nutritional status during pregnancy is potentially a powerful contributor to the intrauterine environment, and may alter offspring physiology and later life cardio-metabolic risk. Putative early life markers of cardio-metabolic risk include newborn body fatness and cardiac autonomic control. We sought to determine whether maternal dietary carbohydrate quantity and/or quality during pregnancy are associated with newborn body composition and cardiac autonomic function. Maternal diet during pregnancy was assessed in 142 mother-infant pairs using a validated food frequency questionnaire. Infant adiposity and body composition were assessed at birth using air-displacement plethysmography. Cardiac autonomic function was assessed as heart rate variability. The quantity of carbohydrates consumed during pregnancy, as a percentage of total energy intake, was not associated with meaningful differences in offspring birth weight, adiposity or heart rate variability (p > 0.05). There was some evidence that maternal carbohydrate quality, specifically higher fibre and lower glycemic index, is associated with higher heart rate variability in the newborn offspring (p = 0.06). This suggests that poor maternal carbohydrate quality may be an important population-level inter-generational risk factor for later cardiac and hemodynamic risk of their offspring.
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Affiliation(s)
- Kirsty M Mckenzie
- Boden Institute of Obesity, Nutrition, Exercise & Eating Disorders, D17-Charles Perkins Centre, University of Sydney, Camperdown, NSW 2006, Australia.
- Sydney Medical School, D17-Charles Perkins Centre, University of Sydney, Camperdown, NSW 2006, Australia.
| | - Hasthi U Dissanayake
- Boden Institute of Obesity, Nutrition, Exercise & Eating Disorders, D17-Charles Perkins Centre, University of Sydney, Camperdown, NSW 2006, Australia.
- Sydney Medical School, D17-Charles Perkins Centre, University of Sydney, Camperdown, NSW 2006, Australia.
| | - Rowena McMullan
- Boden Institute of Obesity, Nutrition, Exercise & Eating Disorders, D17-Charles Perkins Centre, University of Sydney, Camperdown, NSW 2006, Australia.
- Sydney Medical School, D17-Charles Perkins Centre, University of Sydney, Camperdown, NSW 2006, Australia.
- Royal Prince Alfred Hospital, Missenden Road, Camperdown, NSW 2050, Australia.
| | - Ian D Caterson
- Boden Institute of Obesity, Nutrition, Exercise & Eating Disorders, D17-Charles Perkins Centre, University of Sydney, Camperdown, NSW 2006, Australia.
| | - David S Celermajer
- Sydney Medical School, D17-Charles Perkins Centre, University of Sydney, Camperdown, NSW 2006, Australia.
- Royal Prince Alfred Hospital, Missenden Road, Camperdown, NSW 2050, Australia.
| | - Adrienne Gordon
- Sydney Medical School, D17-Charles Perkins Centre, University of Sydney, Camperdown, NSW 2006, Australia.
- Royal Prince Alfred Hospital, Missenden Road, Camperdown, NSW 2050, Australia.
| | - Jonathan Hyett
- Sydney Medical School, D17-Charles Perkins Centre, University of Sydney, Camperdown, NSW 2006, Australia.
| | - Alice Meroni
- Boden Institute of Obesity, Nutrition, Exercise & Eating Disorders, D17-Charles Perkins Centre, University of Sydney, Camperdown, NSW 2006, Australia.
| | - Melinda Phang
- Boden Institute of Obesity, Nutrition, Exercise & Eating Disorders, D17-Charles Perkins Centre, University of Sydney, Camperdown, NSW 2006, Australia.
| | - Camille Raynes-Greenow
- Sydney School of Public Health, Edward Ford Building, Fisher Road, University of Sydney, Sydney, NSW 2006, Australia.
| | - Jaimie W Polson
- Sydney Medical School, D17-Charles Perkins Centre, University of Sydney, Camperdown, NSW 2006, Australia.
- School of Medical Science & Bosch Institute, Anderson Stuart Building (F13), University of Sydney, Sydney, NSW 2006, Australia.
| | - Michael R Skilton
- Boden Institute of Obesity, Nutrition, Exercise & Eating Disorders, D17-Charles Perkins Centre, University of Sydney, Camperdown, NSW 2006, Australia.
- Sydney Medical School, D17-Charles Perkins Centre, University of Sydney, Camperdown, NSW 2006, Australia.
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10
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Ritchie HE, Prestipino L, Polson JW. Dofetilide exposure during pregnancy is associated with high blood pressure in the adult offspring. Reprod Toxicol 2017. [DOI: 10.1016/j.reprotox.2017.06.065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Furlong TM, McDowall LM, Horiuchi J, Polson JW, Dampney RAL. The effect of air puff stress on c-Fos expression in rat hypothalamus and brainstem: central circuitry mediating sympathoexcitation and baroreflex resetting. Eur J Neurosci 2014; 39:1429-38. [DOI: 10.1111/ejn.12521] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2013] [Revised: 01/16/2014] [Accepted: 01/21/2014] [Indexed: 11/27/2022]
Affiliation(s)
- Teri M. Furlong
- School of Medical Sciences (Physiology) and Bosch Institute for Biomedical Research; University of Sydney; Sydney NSW Australia
| | - Lachlan M. McDowall
- School of Medical Sciences (Physiology) and Bosch Institute for Biomedical Research; University of Sydney; Sydney NSW Australia
| | - Jouji Horiuchi
- School of Medical Sciences (Physiology) and Bosch Institute for Biomedical Research; University of Sydney; Sydney NSW Australia
| | - Jaimie W. Polson
- School of Medical Sciences (Physiology) and Bosch Institute for Biomedical Research; University of Sydney; Sydney NSW Australia
| | - Roger A. L. Dampney
- School of Medical Sciences (Physiology) and Bosch Institute for Biomedical Research; University of Sydney; Sydney NSW Australia
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12
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Polson JW, Bekric L, Garnsey M, Dissanayake H, Dampney RAL. An anterograde transport study of the descending projections of the central nucleus of the inferior colliculus. FASEB J 2013. [DOI: 10.1096/fasebj.27.1_supplement.lb844] [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: 11/11/2022]
Affiliation(s)
- Jaimie W Polson
- School of Medical SciencesUniversity of SydneySydneyAustralia
| | - Lejla Bekric
- School of Medical SciencesUniversity of SydneySydneyAustralia
| | - Miles Garnsey
- School of Medical SciencesUniversity of SydneySydneyAustralia
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Iigaya K, Horiuchi J, McDowall LM, Lam ACB, Sediqi Y, Polson JW, Carrive P, Dampney RAL. Blockade of orexin receptors with Almorexant reduces cardiorespiratory responses evoked from the hypothalamus but not baro- or chemoreceptor reflex responses. Am J Physiol Regul Integr Comp Physiol 2012; 303:R1011-22. [DOI: 10.1152/ajpregu.00263.2012] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Orexin neurons form a restricted group in the dorsal hypothalamus. The group is centered on the perifornical area within the classic hypothalamic defense area, an area which when activated produces marked cardiovascular and respiratory effects. Central administration of orexin can produce cardiorespiratory effects, but the extent to which orexin contributes to such responses evoked from the perifornical hypothalamus is not clear. To determine this, we used the dual orexin receptor antagonist Almorexant to challenge the cardiorespiratory effects evoked by disinhibition of the perifornical hypothalamus. Bicuculline (10 and 20 pmol) was microinjected in the perifornical area before and after administration of Almorexant (15 mg/kg iv) or vehicle in urethane-anesthetized rats. Almorexant significantly reduced the pressor, tachycardic, renal sympathoexcitatory, and tachypneic responses to bicuculline (10 pmol, by 55%, 53%, 28%, 77%; 20 pmol, by 54%, 27%, 51%, 72%, respectively). Reductions of similar magnitude were observed with bicuculline microinjections centered on more caudal sites just peripheral to the orexin neuron group, which would likely have activated fewer orexin neurons. In contrast, Almorexant had no effect on the cardiorespiratory response of the chemoreflex (sodium cyanide injection) or the sympathetic component of the baroreflex. Thus orexin makes a major contribution to the cardiorespiratory response evoked from the perifornical area even though orexin neurons represent only a fraction of the output of this area. Orexin neurons may also mediate cardiorespiratory responses from non-orexin neurons in the caudal hypothalamus. However, under resting conditions, blockade of orexin receptors does not affect the chemo- and baroreflexes.
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Affiliation(s)
- Kamon Iigaya
- School of Medical Sciences and Bosch Institute for Biomedical Research, University of Sydney, New South Wales, Australia; and
| | - Jouji Horiuchi
- School of Medical Sciences and Bosch Institute for Biomedical Research, University of Sydney, New South Wales, Australia; and
| | - Lachlan M. McDowall
- School of Medical Sciences and Bosch Institute for Biomedical Research, University of Sydney, New South Wales, Australia; and
| | - Alex C. B. Lam
- School of Medical Sciences and Bosch Institute for Biomedical Research, University of Sydney, New South Wales, Australia; and
| | - Yusuf Sediqi
- School of Medical Sciences and Bosch Institute for Biomedical Research, University of Sydney, New South Wales, Australia; and
| | - Jaimie W. Polson
- School of Medical Sciences and Bosch Institute for Biomedical Research, University of Sydney, New South Wales, Australia; and
| | - Pascal Carrive
- School of Medical Sciences, University of New South Wales, New South Wales, Australia
| | - Roger A. L. Dampney
- School of Medical Sciences and Bosch Institute for Biomedical Research, University of Sydney, New South Wales, Australia; and
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14
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Polson JW, Bisterbosch HM, Panahi SE, Dampney RAL. Prenatal dexamethasone produces altered cardiovascular and autonomic responses to psychological stress. FASEB J 2012. [DOI: 10.1096/fasebj.26.1_supplement.lb793] [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: 11/11/2022]
Affiliation(s)
- Jaimie W Polson
- School of Medical Sciences & Bosch InstituteThe University of SydneySydneyAustralia
| | | | - S Ehsan Panahi
- School of Medical Sciences & Bosch InstituteThe University of SydneySydneyAustralia
| | - Roger AL Dampney
- School of Medical Sciences & Bosch InstituteThe University of SydneySydneyAustralia
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15
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Kenny D, Polson JW, Martin RP, Caputo M, Wilson DG, Cockcroft JR, Paton JF, Wolf AR. Relationship of aortic pulse wave velocity and baroreceptor reflex sensitivity to blood pressure control in patients with repaired coarctation of the aorta. Am Heart J 2011; 162:398-404. [PMID: 21835303 DOI: 10.1016/j.ahj.2011.03.029] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2011] [Accepted: 03/21/2011] [Indexed: 10/18/2022]
Abstract
BACKGROUND Increased aortic stiffness and reduced baroreceptor reflex sensitivity have been described independently after coarctation of the aorta (CoA) repair. This study sought to determine the relationship between these variables and blood pressure control in adolescents after early CoA repair. METHODS Spontaneous baroreceptor reflex sensitivity (sBRS) and aortic pulse wave velocity (PWV) were measured in 29 adolescents after CoA repair and compared with 20 age-matched controls. Patients treated for hypertension or having residual aortic narrowing were excluded. Ambulatory blood pressure (ABP), heart rate variability, and cardiac output were also recorded. After ABP measurement, CoA subjects were classified as normotensive or hypertensive. RESULTS Nine patients (31%) were hypertensive according to standard definitions, and this subgroup had higher aortic PWV than the normotensive subgroup (P = .004). There was a significant positive correlation between ABP and PWV seen in the whole CoA group (r(2) = 0.5, P < .01). The normotensive subgroup had increased sBRS compared with controls (P = .02). This difference was not seen between the hypertensive subgroup and controls. There was a significant inverse relationship between sBRS and aortic PWV in the whole CoA group (r(2) = 0.25, P = .01). The normotensive subgroup had a significant reduction in stroke index compared with controls (P = .02), which was not seen in the hypertensive subgroup (P = .96). CONCLUSIONS Adolescents with hypertension after CoA repair have increased aortic PWV and a relative reduction in sBRS compared with normotensive CoA patients. Thus, failure of the baroreceptor reflex to compensate for increasing arterial stiffness may herald the onset of hypertension in these patients.
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16
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Kenny D, Polson JW, Martin RP, Paton JFR, Wolf AR. Hypertension and coarctation of the aorta: an inevitable consequence of developmental pathophysiology. Hypertens Res 2011; 34:543-7. [PMID: 21412243 DOI: 10.1038/hr.2011.22] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [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
Patients with coarctation of the aorta develop early onset hypertension in spite of early effective repair. This is associated with significant morbidity and is arguably the single most important outcome variable in this patient group. We discuss the potential pathophysiological mechanisms involved in the development of hypertension with clinical reference to monozygotic twins, and review potential strategies for therapy and prevention in this setting.
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Affiliation(s)
- Damien Kenny
- Bristol Congenital Heart Center, Bristol Royal Hospital for Children, Bristol, UK
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17
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Kenny D, Polson JW, Martin RP, Wilson DG, Caputo M, Cockcroft JR, Paton JF, Wolf AR. Surgical Approach for Aortic Coarctation Influences Arterial Compliance and Blood Pressure Control. Ann Thorac Surg 2010; 90:600-4. [DOI: 10.1016/j.athoracsur.2010.04.098] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2010] [Revised: 04/27/2010] [Accepted: 04/27/2010] [Indexed: 01/22/2023]
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18
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Sun C, Zubcevic J, Polson JW, Potts JT, Diez-Freire C, Zhang Q, Paton JFR, Raizada MK. Shift to an involvement of phosphatidylinositol 3-kinase in angiotensin II actions on nucleus tractus solitarii neurons of the spontaneously hypertensive rat. Circ Res 2009; 105:1248-55. [PMID: 19850939 DOI: 10.1161/circresaha.109.208926] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
RATIONALE Central angiotensin (Ang) II inhibits baroreflex and plays an important role in the pathogenesis of hypertension. However, the underlying molecular mechanisms are still not fully understood. OBJECTIVE Our objective in the present study was to characterize the signal transduction mechanism of phosphatidylinositol 3-kinase (PI3K) involvement in Ang II-induced stimulation of central neuronal activity in cultured neurons and Ang II-induced inhibition of baroreflex in spontaneously hypertensive rats (SHR) versus WKY rats. METHODS AND RESULTS Application of Ang II to neurons produced a 42% greater increase in neuronal firing in cells from the SHR than the WKY rat. Although the Ang II-mediated increase in firing rate was abolished entirely by the protein kinase (PK)C inhibitor GF109230 in the WKY, blockade of both PKC and PI3K activity was necessary in the SHR. This was associated with an increased ability of Ang II to stimulate NADPH oxidase-reactive oxygen species (ROS)-mediated signaling involving phosphorylation of the p47phox subunit of the NADPH oxidase and was dependent on the activation of PI3K in the SHR. Inhibition of PI3K resulted in the reduction of levels of p47phox phosphorylation, NADPH oxidase activity, ROS levels, and ultimately neuronal activity in cells from the SHR but not the WKY rat. In addition, in working heart-brainstem preparations, inhibition of PKC activity in the nucleus of the solitary tract in situ abolished the Ang II-mediated depression of cardiac and sympathetic baroreceptor reflex gain in the WKY. In contrast, PKC inhibition in the nucleus of the solitary tract of SHR only partially reduced the effect of Ang II on the baroreceptor reflex gain. CONCLUSIONS These observations demonstrate that PI3K in the cardiovascular brainstem regions of the SHR may be selectively involved in Ang II-mediated signaling that includes a reduction in baroreceptor reflex function, presumably via a NADPH-ROS mediated pathway.
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Affiliation(s)
- Chengwen Sun
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, FL 32610, USA
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19
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Kenny D, Polson JW, Martin RP, Paton JF, Wolf AR. Normalization of Autonomic Function in Children With Coarctation of the Aorta After Surgical Correction in Infancy. Hypertension 2009; 54:e21-2. [DOI: 10.1161/hypertensionaha.109.136481] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Damien Kenny
- Bristol Congenital Heart Center, Bristol Royal Hospital for Children, Bristol, United Kingdom
| | - Jaimie W. Polson
- Department of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom
| | - Robin P. Martin
- Bristol Congenital Heart Center, Bristol Royal Hospital for Children, Bristol, United Kingdom
| | - Julian F.R. Paton
- Department of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom
| | - Andrew R. Wolf
- Department of Anesthesia, Bristol Royal Hospital for Children, Bristol, United Kingdom
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20
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Waki H, Shimizu T, Yamasaki M, Katahira K, Katsuda S, Polson JW, Maeda M. Ramp rate of blood pressure changes does not affect aortic afferent sensitivity in anesthetized rats. Neurosci Lett 2008; 448:37-40. [DOI: 10.1016/j.neulet.2008.10.037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2008] [Revised: 10/09/2008] [Accepted: 10/13/2008] [Indexed: 11/17/2022]
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21
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Zubcevic J, Polson JW, Kasparov S, Diez‐Freire CC, Raizada MK, Paton JF. Role of phosphoinositide‐3‐kinase (PI3K) in the nucleus of the solitary tract (NTS) in the modulation of baroreceptor reflex function in the hypertensive rat. FASEB J 2008. [DOI: 10.1096/fasebj.22.1_supplement.737.34] [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: 11/11/2022]
Affiliation(s)
- Jasenka Zubcevic
- Physiology and PharmacologyUniversity of BristolBristolUnited Kingdom
| | - Jaimie W Polson
- Physiology and PharmacologyUniversity of BristolBristolUnited Kingdom
| | - Sergey Kasparov
- Physiology and PharmacologyUniversity of BristolBristolUnited Kingdom
| | - Carlos C Diez‐Freire
- Department of Physiology and Functional GenomicsUniversity of FloridaGainesvilleFL
| | - Mohan K Raizada
- Department of Physiology and Functional GenomicsUniversity of FloridaGainesvilleFL
| | - Julian F.R. Paton
- Physiology and PharmacologyUniversity of BristolBristolUnited Kingdom
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22
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Polson JW, Dampney RAL, Boscan P, Pickering AE, Paton JFR. Differential baroreflex control of sympathetic drive by angiotensin II in the nucleus tractus solitarii. Am J Physiol Regul Integr Comp Physiol 2007; 293:R1954-60. [PMID: 17804587 DOI: 10.1152/ajpregu.00041.2007] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [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: 02/07/2023]
Abstract
Microinjection of angiotensin II into the nucleus tractus solitarii attenuates the baroreceptor reflex-mediated bradycardia by inhibiting both vagal and cardiac sympathetic components. However, it is not known whether the baroreflex modulation of other sympathetic outputs (i.e., noncardiac) also are inhibited by exogenous angiotensin II (ANG II) in nucleus tractus solitarii (NTS). In this study, we determined whether there was a difference in the baroreflex sensitivity of sympathetic outflows at the thoracic and lumbar levels of the sympathetic chain following exogenous delivery of ANG II into the NTS. Experiments were performed in two types of in situ arterially perfused decerebrate rat preparations. Sympathetic nerve activity was recorded from the inferior cardiac nerve, the midthoracic sympathetic chain, or the lower thoracic-lumbar sympathetic chain. Increases in perfusion pressure produced a reflex bradycardia and sympathoinhibition. Microinjection of ANG II (500 fmol) into the NTS attenuated the reflex bradycardia (57% attenuation, P < 0.01) and sympathoinhibition of both the inferior cardiac nerve (26% attenuation, P < 0.05) and midthoracic sympathetic chain (37% attenuation, P < 0.05) but not the lower thoracic-lumbar chain (P = 0.56). We conclude that ANG II in the nucleus tractus solitarii selectively inhibits baroreflex responses in specific sympathetic outflows, possibly dependent on the target organ innervated.
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Affiliation(s)
- J W Polson
- Dept. of Physiology, Bristol Heart Institute, School of Medical Science, University of Bristol, Bristol BS8 1TD, UK
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23
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Polson JW, Paton JF, Wolf AR. Altered autonomic function in programmed hypertension following gestational administration of glucocorticoid. Auton Neurosci 2007. [DOI: 10.1016/j.autneu.2007.06.258] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Abstract
Background—
Coarctation of the aorta (CoA) is associated with hypertension and abnormalities of blood pressure control, which persist after late repair. Assumptions that neonatal repair would prevent development of blood pressure abnormalities have not been supported by recent data. We hypothesized that early pathological adjustment of autonomic cardiovascular function may already be established in the neonate with coarctation.
Methods and Results—
We studied 8 otherwise well neonates with simple CoA and compared measures of spontaneous baroreflex sensitivity, heart rate variability, and blood pressure variability with 13 healthy newborn babies. Spontaneous baroreflex sensitivity was calculated with sequence methodology from an ECG, and noninvasive blood pressure was recorded with a Portapres. Heart rate variability was determined with time- and frequency-domain measures. Blood pressure variability was measured in the frequency domain. In comparison with normal controls, neonates with CoA had raised blood pressure (78.9±3.8 versus 67.1±2.1 mm Hg), depressed baroreflex sensitivity (8.7±1.5 versus 13.8±1.1 ms/mm Hg), reduced heart rate variability (total power 16.5±3.1 versus 31.5±2.2 ms
2
), and an increase in the high-frequency component of blood pressure variability (3.1±0.3 versus 2.2±0. 2 mm Hg
2
). This is not the pattern expected if neonates with CoA simply had subclinical cardiac failure.
Conclusions—
These data suggest that infants with CoA already show signs of pathological adjustment of autonomic cardiovascular homeostasis. Further longitudinal studies are required to determine whether these alterations play a role in the increased risk of late hypertension in these patients.
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Affiliation(s)
- Jaimie W Polson
- Department of Clinical Sciences at South Bristol, School of Medical Sciences, Bristol Heart Institute, University of Bristol, Bristol, United Kingdom
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25
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Waki H, Katahira K, Polson JW, Kasparov S, Murphy D, Paton JFR. Automation of analysis of cardiovascular autonomic function from chronic measurements of arterial pressure in conscious rats. Exp Physiol 2005; 91:201-13. [PMID: 16239254 DOI: 10.1113/expphysiol.2005.031716] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
At present, there is no single software package that provides a comprehensive power spectral analysis of pulse interval (PI) and arterial blood pressure (BP), spontaneous cardiac baroreceptor reflex gain (sBRG) and respiratory rate. Furthermore, scientific validation of the software that is currently commercially available and employed has not been published. We introduce 'Hey-Presto' software, which fully evaluates cardiovascular autonomic function from the BP signal obtained from rats. The program performs power spectral analysis of HR and BP variability, respiratory rate and, based on a time-series method, spontaneous cardiac baroreceptor (sBRG). We have validated Hey-Presto with conventional pharmacological agents to block cardiac vagal and cardiac sympathetic transmission in conscious rats fitted with a radio-telemetery BP transducer. Following administration of atropine (1 mg kg(-1), I.V.), high-frequency (HF) power of the PI decreased (P < 0.01) and was associated with the expected increase in HR. Subsequent cardiac sympathetic blockade (atenolol, 1 mg kg(-1), I.V.) reduced the low frequency (LF) to HF ratio (LF:HF) of the PI (P < 0.01), which was consistent with the observed reduction in HR. We also found that alterations in sBRG after blockade of cardiac autonomic transmission were highly comparable to values computed manually using vasoactive drugs administered intravenously. The software also detected circadian rhythms in sBRG, HF component of the PI, LF:HF of the PI and LF component of the BP as well as BP and HR during continuous 24 h recording. By demonstrating its application to humans, we found appropriate changes in the power of PI and the LF power of the BP during postural changes. These results demonstrate that Hey-Presto allows a fully automated, reliable, fast and comprehensive evaluation of cardiovascular autonomic function based on chronic measurements of BP in rats. Moreover, we have confirmed its versatility by demonstrating its application to man.
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Affiliation(s)
- Hidefumi Waki
- Department of Physiology, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK.
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26
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Dampney RAL, Polson JW, Potts PD, Hirooka Y, Horiuchi J. Functional organization of brain pathways subserving the baroreceptor reflex: studies in conscious animals using immediate early gene expression. Cell Mol Neurobiol 2004; 23:597-616. [PMID: 14514018 DOI: 10.1023/a:1025080314925] [Citation(s) in RCA: 134] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
1. This paper reviews studies carried out in our laboratory in which we have used the c-fos functional mapping method, in combination with other methods, to determine the functional organization of central baroreceptor pathways as they operate in the conscious rabbit. 2. First, we showed that periods of induced hypertension or hypotension each result in a specific and reproducible pattern of activation of neurons in the brainstem and forebrain. In particular, hypotension (but not hypertension) results in the activation of catecholamine neurons in the medulla and pons and vasopressin-synthesizing neurons in the hypothalamus. 3. The activation of medullary cell groups in response to induced hypertension or hypotension in the conscious rabbit is almost entirely dependent on inputs from arterial baroreceptors, while the activation of hypothalamic vasopressin-synthesising neurons in response to hypotension is largely dependent on baroreceptors, although an increase in circulating angiotensin also appears to contribute. 4. Discrete groups of neurons in the rostral ventrolateral medulla (RVLM) and A5 area in the pons are the major groups of spinally projecting neurons activated by baroreceptor unloading. In contrast, spinally projecting neurons in the paraventricular nucleus in the hypothalamus appear to be largely unaffected by baroreceptor signals. 5. Direct afferent inputs to RVLM neurons in response to increases or decreases in arterial pressure originate primarily from other medullary nuclei, particularly neurons located in the caudal and intermediate levels of the ventrolateral medulla (CVLM and IVLM), as well as in the nucleus tractus solitarius (NTS). 6. There is also a direct projection from barosensory neurons in the NTS to the CVLM/IVLM region, which is activated by baroreceptor inputs. 7. Collectively, the results of our studies in conscious animals indicate that baroreceptor signals reach all levels of the brain. With regard to the baroreceptor reflex control of sympathetic activity, our studies are consistent with previous studies in anesthetized animals, but in addition reveal other previously unrecognized pathways that also contribute to this reflex regulation.
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Affiliation(s)
- Roger A L Dampney
- Department of Physiology, Institute for Biomedical Research, University of Sydney, Sydney, New South Wales, Australia.
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27
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Marsh AJ, Fontes MAP, Killinger S, Pawlak DB, Polson JW, Dampney RAL. Cardiovascular responses evoked by leptin acting on neurons in the ventromedial and dorsomedial hypothalamus. Hypertension 2003; 42:488-93. [PMID: 12939234 DOI: 10.1161/01.hyp.0000090097.22678.0a] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Leptin, a circulating hormone produced by adipose tissue, is believed to act on the hypothalamus to increase sympathetic vasomotor activity, in addition to its well-known effects on appetite and energy expenditure. In this study, we determined the cardiovascular effects of direct application of leptin to specific cell groups within the hypothalamus that are known to be activated by circulating leptin. In rats anesthetized with urethane, microinjections of leptin (16 ng in 20 nL solution) were made into the ventromedial hypothalamic nucleus, dorsomedial hypothalamic nucleus, and paraventricular nucleus. Compared with vehicle solution, microinjections of leptin into the ventromedial hypothalamic nucleus evoked significant increases in arterial pressure and renal sympathetic nerve activity, but not heart rate. In contrast, microinjections of leptin into the dorsomedial hypothalamic nucleus evoked significant increases in arterial pressure and heart rate but not renal sympathetic nerve activity, whereas microinjections of leptin into the paraventricular nucleus had no significant effect on any of the measured cardiovascular variables. These results indicate that the ventromedial and dorsomedial hypothalamic regions might be important sites at which leptin activation leads to increases in sympathetic vasomotor activity and heart rate, as occurs in obesity-related hypertension.
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Affiliation(s)
- Ainsley J Marsh
- Department of Physiology and Institute for Biomedical Research, University of Sydney, NSW, Australia
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Dampney RAL, Horiuchi J, Tagawa T, Fontes MAP, Potts PD, Polson JW. Medullary and supramedullary mechanisms regulating sympathetic vasomotor tone. Acta Physiol Scand 2003; 177:209-18. [PMID: 12608991 DOI: 10.1046/j.1365-201x.2003.01070.x] [Citation(s) in RCA: 217] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
AIM Neurons in the rostral ventrolateral medulla (RVLM) that project directly to sympathetic preganglionic neurons in the spinal cord play a critical role in maintaining tonic activity in sympathetic vasomotor nerves. Intracellular recordings in vivo from putative RVLM presympathetic neurons have demonstrated that under resting conditions these neurons display an irregular tonic firing rate, and also receive both excitatory and inhibitory synaptic inputs. This paper will briefly review some recent findings on the role of glutamate, GABA and angiotensin II (Ang II) receptors in maintaining the tonic activity of RVLM presympathetic neurons. RESULTS Based on these findings, the following hypotheses will be discussed: (1) RVLM neurons receive tonic glutamatergic excitatory inputs, which originate from both medullary and supramedullary sources; (2) at least some neurons that project to and tonically inhibit RVLM presympathetic neurons are themselves tonically inhibited by GABAergic inputs originating from neurons in the caudalmost part of the ventrolateral medulla (caudal pressor area); (3) under normal conditions, Ang II receptors in the RVLM do not contribute significantly to the tonic activity of RVLM presympathetic neurons, but may do so in abnormal conditions such as heart failure or neurogenic hypertension; (4) RVLM presympathetic neurons maintain a significant level of tonic resting activity even when glutamate, GABA and Ang II receptors on the neurons are completely blocked. Under these conditions, the tonic activity is a consequence either of the intrinsic membrane properties of the neurons (autoactivity) or of synaptic inputs mediated by receptors other than glutamate, GABA or Ang II receptors. CONCLUSION The current evidence indicates that the resting activity of RVLM presympathetic neurons is determined by the balance of powerful tonic excitatory and inhibitory synaptic inputs. Ang II receptors also contribute to the raised resting activity of these neurons in some pathological conditions.
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Affiliation(s)
- R A L Dampney
- Department of Physiology and Institute for Biomedical Research, University of Sydney, New South Wales, Australia
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Abstract
Hypotension produces a reflex increase in the activity of sympathetic vasomotor nerves. Studies in anaesthetised animals have established that neurons in the rostral ventrolateral medulla (RVLM) that project directly to sympathetic vasomotor preganglionic neurons in the spinal cord are a critical component of the central pathways mediating this reflex response. There are also neurons in supramedullary regions (the A5 area in the pons and the paraventricular nucleus (PVN) in the hypothalamus), however, that project directly to the sympathetic vasomotor outflow. The aim of this study was to identify and map neurons within the A5 area and PVN, as well as in the RVLM, which may contribute to the reflex sympathoexcitatory response to a hypotensive challenge in conscious rabbits. In a preliminary operation, a retrogradely transported tracer was injected into a site centred on the intermediolateral cell column in the upper lumbar spinal cord. After a waiting period of at least 1 week, a moderate hypotension (decrease in arterial pressure of approximately 20 mm Hg) was induced in conscious rabbits for 60 min by continuous infusion of sodium nitroprusside. In confirmation of previous studies, hypotension resulted in the expression of Fos in the RVLM, the A5 area and PVN. There were also retrogradely labelled neurons in all these regions. In both the RVLM and A5 area, approximately 40% of the retrogradely labelled neurons were also immunoreactive for Fos. In contrast, in the PVN the proportion of retrogradely labelled neurons that were also Fos-positive was much less (approximately 6%). This study has demonstrated that, in the conscious rabbit, a significant proportion of spinally projecting neurons within discrete regions in the RVLM and A5 area are activated by hypotension (as indicated by Fos expression). In the PVN, only a very small proportion of spinally projecting neurons are activated by hypotension, and thus these neurons appear to be regulated primarily by inputs other than baroreceptor inputs.
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Affiliation(s)
- Jaimie W Polson
- Department of Physiology and Institute for Biomedical Research, University of Sydney, NSW, Australia
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Dampney RAL, Coleman MJ, Fontes MAP, Hirooka Y, Horiuchi J, Li YW, Polson JW, Potts PD, Tagawa T. Central mechanisms underlying short- and long-term regulation of the cardiovascular system. Clin Exp Pharmacol Physiol 2002; 29:261-8. [PMID: 11985533 DOI: 10.1046/j.1440-1681.2002.03640.x] [Citation(s) in RCA: 226] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
1. Sympathetic vasomotor nerves play a major role in determining the level of arterial blood pressure and the distribution of cardiac output. The present review will discuss briefly the central regulatory mechanisms that control the sympathetic outflow to the cardiovascular system in the short and long term. 2. In the short term, the sympathetic vasomotor outflow is regulated by: (i) homeostatic feedback mechanisms, such as the baroreceptor or chemoreceptor reflexes; or (ii) feed-forward mechanisms that evoke cardiovascular changes as part of more complex behavioural responses. 3. The essential central pathways that subserve the baroreceptor reflex and, to a lesser extent, other cardiovascular reflexes, have been identified by studies in both anaesthetized and conscious animals. A critical component of these pathways is a group of neurons in the rostral ventrolateral medulla that project directly to the spinal sympathetic outflow and that receive inputs from both peripheral receptors and higher centres in the brain. 4. Much less is known about the central pathways subserving feed-forward or 'central command' responses, such as the cardiovascular changes that occur during exercise or that are evoked by a threatening or alerting stimulus. However, recent evidence indicates that the dorsomedial hypothalamic nucleus is a critical component of the pathways mediating the cardiovascular response to an acute alerting stimulus. 5. Long-term sustained changes in sympathetic vasomotor activity occur under both physiological conditions (e.g. a change in salt intake) and pathophysiological conditions (e.g. heart failure). There is evidence that the paraventricular nucleus in the hypothalamus is a critical component of the pathways mediating these changes. 6. Understanding the central mechanisms involved in the long-term regulation of sympathetic activity and blood pressure is a major challenge for the future. As a working hypothesis, a model is presented of the postulated central mechanisms that result in sustained changes in sympathetic vasomotor activity that are evoked by different types of chronic stimulation.
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Affiliation(s)
- R A L Dampney
- Department of Physiology and Institute for Biomedical Research, University of Sydney, Sydney, New South Wales, Australia.
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Abstract
Physiological and anatomic methods were used to determine whether neurons in the rostral ventrolateral medulla (RVLM), nucleus tractus solitarius (NTS), or hypothalamic paraventricular nucleus (PVN) mediate the cardiovascular response evoked from the dorsomedial hypothalamic nucleus (DMH), which is believed to play a key role in mediating responses to stress. In urethane-anesthetized rats, activation of neurons in the DMH by microinjection of bicuculline resulted in a large increase in arterial pressure, heart rate, and renal sympathetic nerve activity. The pressor and sympathoexcitatory responses, but not the tachycardic response, were greatly reduced after bilateral muscimol injections into the RVLM even when baseline arterial pressure was maintained at a constant level. These responses were not reduced by muscimol injections into the PVN or NTS. Retrograde tracing experiments identified many neurons in the DMH that projected directly to the RVLM. The results indicate that the vasomotor and cardiac components of the response evoked from the DMH are mediated by pathways that are dependent and independent, respectively, of neurons in the RVLM.
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Affiliation(s)
- M A Fontes
- Department of Physiology and Institute for Biomedical Research, University of Sydney, New South Wales 2006, Australia.
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Takeda M, Phillips JK, Dubey R, Polson JW, Lipski J. Modulation of ACh-induced currents in rat adrenal chromaffin cells by ligands of alpha2 adrenergic and imidazoline receptors. Auton Neurosci 2001; 88:151-9. [PMID: 11474556 DOI: 10.1016/s1566-0702(01)00221-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The aim of this study was to investigate the expression of the alpha2-adrenergic receptors in the adrenal medulla, and to examine the mechanism by which clonidine and related drugs inhibit acetylcholine (ACh)-induced whole-cell currents in adrenal chromaffin cells. Reverse transcription-polymerase chain reaction (RT-PCR) performed on punches of rat adrenal medulla demonstrated expression of mRNA for the 2A-, alpha2B- and alpha2C-adrenergic receptors. Similar experiments conducted with tissue punches obtained from the adrenal cortex did not reveal expression of these receptor subtypes. Whole-cell currents were recorded in isolated chromaffin cells using the perforated-patch configuration. ACh (50 microM) evoked inward currents with a peak amplitude of 117.8+/-9.3 pA (n = 45; Vhol = -60 mV). The currents were inhibited in a dose-dependent manner (0.5-50 microM) by clonidine, UK 14,304 and rilmenidine (agonists of alpha2/imidazoline receptors), as well as by SKF 86466 and efaroxan (antagonists). Adrenaline and noradrenaline (50-100 microM) had no significant effect. Thus, although the adrenal medulla expresses mRNA for the alpha2-adrenergic receptors, the lack of agonist-antagonist specificity observed in our whole-cell recordings (in the absence of intracellular dialysis) provides additional evidence against the possibility that these inhibitory effects are mediated by classical alpha2 or imidazoline receptor interactions.
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Affiliation(s)
- M Takeda
- Department of Physiology, Faculty of Medicine and Health Science, University of Auckland, New Zealand
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Dampney RA, Tagawa T, Horiuchi J, Potts PD, Fontes M, Polson JW. What drives the tonic activity of presympathetic neurons in the rostral ventrolateral medulla? Clin Exp Pharmacol Physiol 2000; 27:1049-53. [PMID: 11117229 DOI: 10.1046/j.1440-1681.2000.03375.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
1. The present review discusses the mechanisms that maintain the tonic activity of presympathetic cardiovascular neurons in the rostral part of the ventrolateral medulla. 2. Experimental evidence is reviewed that indicates that these neurons receive both tonic excitatory and tonic inhibitory synaptic inputs. The former appear to be mediated, at least in part, by glutamate receptors and the latter appear to be mediated by GABA receptors. 3. There is also evidence that these neurons have the capacity to generate action potentials in the absence of synaptic inputs. However, at present, there is not clear evidence that such an intrinsic pacemaker-like mechanism contributes to the tonic activity of these neurons under normal resting conditions. 4. These neurons are also chemosensitive and this may contribute to their tonic activation under conditions of hypoxia or hypercapnia.
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Affiliation(s)
- R A Dampney
- Department of Physiology and Institute for Biomedical Research, University of Sydney, New South Wales, Australia.
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Horiuchi J, Potts PD, Polson JW, Dampney RA. Distribution of neurons projecting to the rostral ventrolateral medullary pressor region that are activated by sustained hypotension. Neuroscience 1999; 89:1319-29. [PMID: 10362317 DOI: 10.1016/s0306-4522(98)00399-6] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Hypotension produces a reflex increase in the activity of sympathetic vasomotor and cardiac nerves. It is believed that the reflex sympathoexcitation is due largely to disinhibition of sympathoexcitatory neurons in the rostral ventrolateral medulla, but it is possible that it may also be mediated by excitatory inputs from interneurons that are activated by a fall in blood pressure. The aim of this study in conscious rabbits was to identify and map neurons with properties that are characteristic of interneurons conveying excitatory inputs to the rostral ventrolateral medullary pressor region in response to hypotension. In a preliminary operation, a retrogradely-transported tracer, fluorescent-labelled microspheres, was injected into the functionally-identified pressor region in the rostral ventrolateral medulla. After a waiting period of at least one week, a moderate hypotension (decrease in arterial pressure of approximately 20 mmHg) was induced in conscious rabbits for 60 min by the continuous infusion of sodium nitroprusside. In confirmation of a previous study from our laboratory, [Li and Dampney (1994) Neuroscience 61, 613634] hypotension resulted in the expression of Fos (the protein product of c-fos, a marker of neuronal activation) in many neurons in several distinct regions in the brainstem and hypothalamus. Some of these regions (nucleus tractus solitarius, area postrema, caudal and intermediate ventrolateral medulla, parabrachial complex in the pons, and paraventricular nucleus in the hypothalamus) also contained large numbers of retrogradely-labelled cells. Approximately 10% of the Fos-positive neurons in the nucleus tractus solitarius, and 15-20% of Fos-positive neurons in the caudal and intermediate ventrolateral medulla were also retrogradely-labelled from the rostral ventrolateral medullary pressor region. In other brain regions, very few double-labelled neurons were found. In previous studies from our laboratory, we have determined the distribution of neurons in the brainstem that project to the rostral ventrolateral medullary pressor region and that are also activated by hypertension [Polson et al. (1995) Neuroscience 67, 107-123] or by hypoxia. [Hirooka et al. (1997) Neuroscience 80, 1209-1224] Comparison of the present results with those from these previous studies indicate that although hypotension and hypoxia both elicit powerful reflex sympathoexcitatory responses, the central pathways subserving these effects in conscious animals are fundamentally different. Hypoxia activates rostral ventrolateral medullary sympathoexcitatory neurons mainly via a major direct excitatory projection from the nucleus tractus solitarius, as well as from the Kölliker-Fuse nucleus in the pons, while in contrast the activation of these neurons in response to hypotension appears to be due mainly to disinhibition, mediated via inhibitory interneurons. In addition, however, inputs originating from excitatory interneurons in the nucleus tractus solitarius and caudal and intermediate parts of the ventrolateral medulla appear to contribute to the hypotension-evoked activation of sympathoexcitatory neurons in the rostral ventrolateral medulla.
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Affiliation(s)
- J Horiuchi
- Department of Physiology and Institute for Biomedical Research, University of Sydney, New South Wales, Australia
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Hirooka Y, Polson JW, Potts PD, Dampney RA. Hypoxia-induced Fos expression in neurons projecting to the pressor region in the rostral ventrolateral medulla. Neuroscience 1997; 80:1209-24. [PMID: 9284071 DOI: 10.1016/s0306-4522(97)00111-5] [Citation(s) in RCA: 110] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Previous studies in anaesthetized animals have shown that the hypoxia-induced increase in sympathetic vasomotor activity is largely dependent on synaptic excitation of sympathoexcitatory pressor neurons in the rostral part of the ventrolateral medulla. The primary aim of this study was to determine, in conscious rabbits, the distribution of neurons within the brain that have properties characteristic of interneurons conveying excitatory inputs to the rostral ventrolateral medullary pressor region in response to systemic hypoxia. In a preliminary operation, a retrogradely-transported tracer, fluorescent-labelled microspheres, was injected into the physiologically-identified pressor region in the rostral ventrolateral medulla. After a waiting period of one to two weeks, the conscious rabbits were subjected to moderate hypoxia (induced by breathing 10% O2 in N2) for a period of 60 min. Control groups of animals were exposed to room air or to mild hypoxia (12% O2 in N2). Moderate hypoxia resulted in a modest hypertension of approximately 15 mmHg, and in the expression of Fos (a marker of neuronal activation) in many neurons in the nucleus tractus solitarius, the rostral, intermediate and caudal parts of the ventrolateral medulla, the Kölliker-Fuse nucleus, locus coeruleus, subcoeruleus and A5 area in the pons as well as in several midbrain and forebrain regions, including the periaqueductal grey in the midbrain and the paraventricular, supraoptic and arcuate nuclei in the hypothalamus. Fos expression was also observed in these regions in rabbits subjected to mild hypoxia or normoxia, but it was much reduced compared to rabbits subjected to moderate hypoxia. Approximately half of the neurons in the ventrolateral medulla, 27% of neurons in the nucleus tractus solitarius, and 49-81% of neurons in the locus coeruleus, sub-coeruleus and A5 area that expressed Fos following moderate hypoxia were also immunoreactive for tyrosine hydroxylase, and were therefore catecholamine cells. Approximately half of the neurons in the nucleus tractus solitarius and two-thirds of neurons in the Kölliker-Fuse nucleus that expressed Fos following moderate hypoxia were retrogradely labelled from the rostral ventrolateral medullary pressor region. Similarly, approximately one quarter of Fos-positive cells in the caudal and intermediate ventrolateral medulla were retrogradely labelled, but very few Fos-positive/retrogradely-labelled cells were found in other pontomedullary or suprapontine brain regions. The results indicate that systemic hypoxia results in activation of neurons in several discrete nuclei in the brainstem and forebrain, including neurons in all the major pontomedullary catecholamine cell groups. However, neurons that are activated by systemic hypoxia and that also project to the rostral ventrolateral medullary pressor region are virtually confined to the lower brainstem, primarily in the nucleus tractus solitarius and Kölliker-Fuse nucleus and to a lesser extent the caudal/intermediate ventrolateral medulla. In a previous study from our laboratory, we determined the distribution of neurons in the brainstem that are activated by hypertension and that also project to the rostral ventrolateral medullary pressor region. [Polson et al. (1995) Neuroscience 67, 107-123]. Comparison of the present results with those from this previous study indicates that the hypoxia-activated neurons in the nucleus tractus solitarius and Kölliker-Fuse nucleus that project to the rostral ventrolateral medulla are likely to be interneurons conveying excitatory chemoreceptor signals, while those in the caudal/intermediate ventrolateral medulla are likely to be mainly interneurons conveying inhibitory baroreceptor signals, activated by the rise in arterial blood pressure associated with the hypoxia-induced hypertension.
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Affiliation(s)
- Y Hirooka
- Department of Physiology and Institute for Biomedical Research, University of Sydney, New South Wales, Australia
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Potts PD, Polson JW, Hirooka Y, Dampney RA. Effects of sinoaortic denervation on Fos expression in the brain evoked by hypertension and hypotension in conscious rabbits. Neuroscience 1997; 77:503-20. [PMID: 9472407 DOI: 10.1016/s0306-4522(96)00459-9] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
We have previously shown [Li and Dampney (1994) Neuroscience 61, 613-634] that periods of sustained hypertension and hypotension each induces a distinctive and reproducible pattern of neuronal expression of Fos (a marker of neuronal activation) in specific regions of the brainstem and forebrain of conscious rabbits. The aim of this study was to determine the contribution of afferent inputs from arterial baroreceptors to the activation of neurons in these various brain regions that is caused by a sustained change in arterial pressure. Experiments were carried out on rabbits in which the carotid sinus and aortic depressor nerves were cut in a preliminary operation. Following a recovery period of seven to 10 days, a moderate hypertension or hypotension (increase or decrease in arterial pressure of 20-30 mmHg) was induced in conscious barodenervated rabbits for 60 min by the continuous infusion of phenylephrine or sodium nitroprusside, respectively. In control experiments, barodenervated rabbits were subjected to the identical procedures except that they were infused with the vehicle solution alone. Compared with the effects seen in barointact rabbits, [Li and Dampney (1994) Neuroscience 61, 613-634] the number of neurons that expressed Fos in response to hypertension was reduced by approximately 90% in the nucleus of the solitary tract and in the caudal and intermediate parts of the ventrolateral medulla. In supramedullary regions, baroreceptor denervation resulted in a reduction of approximately 60% in hypertension-induced Fos expression in the central nucleus of the amygdala and in the bed nucleus of the stria terminalis, but no significant reduction in the parabrachial complex in the pons. Following hypotension, the number of neurons that expressed Fos in barodenervated rabbits, compared with barointact rabbits, [Li and Dampney (1994) Neuroscience 61, 613-634] was reduced by approximately 90% in the nucleus of the solitary tract, area postrema, and caudal, intermediate and rostral parts of the ventrolateral medulla. Baroreceptor denervation also resulted in a similar large reduction in hypotension-induced Fos expression in many supramedullary regions (locus coeruleus, midbrain periaqueductal grey, hypothalamic paraventricular nucleus, and in the central nucleus of the amygdala and the bed nucleus of the stria terminalis in the basal forebrain). In the supraoptic nucleus, hypotension-induced Fos expression in barodenervated rabbits was reduced by 75% compared to barointact animals, but was still significantly greater than in control animals. There was also a high level of Fos expression, much greater than in control animals, in the circumventricular organs surrounding the third ventricle (subfornical organ and organum vasculosum lamina terminalis). The results indicate that in conscious rabbits the activation of neurons that occurs in several discrete regions at all levels of the brain following a sustained change in arterial pressure is largely dependent upon inputs from arterial baroreceptors, with the exception of neurons in the circumventricular organs surrounding the third ventricle that are activated by sustained hypotension. The latter group of neurons are known to project to vasopressin-secreting neurons in the supraoptic nucleus, and may therefore via this pathway trigger the hypotension-induced release of vasopressin that occurs in the absence of baroreceptor inputs.
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Affiliation(s)
- P D Potts
- Department of Physiology, University of Sydney, New South Wales, Australia
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Abstract
OBJECTIVE It has been shown that nitric oxide (NO) plays an important role in the central control of arterial pressure and sympathetic nerve activity. The aim of this study was to determine whether NO can regulate sympathetic nerve activity by an action on pressor neurons within the rostral part of the ventrolateral medulla (VLM). DESIGN AND METHODS Experiments were performed on anaesthetized rabbits with denervated arterial and cardiopulmonary baroreceptors. The mean arterial pressure (MAP), heart rate and renal sympathetic nerve activity were measured. Microinjections of the NO donors sodium nitroprusside (SNP, 4-50 nmol) and S-nitroso-glutathione (10 nmol), the NO precursor L-arginine (50 nmol) and the NO synthase inhibitor N omega-nitro-L-arginine methyl ester (L-NAME, 50 nmol), were made into the functionally identified pressor region in the rostral VLM. The effects of SNP were also determined before and after injection of 5 nmol methylene blue into the same area. In control experiments, injections of D-arginine (50 nmol) and D-NAME (50 nmol), which are the inactive isomers of L-arginine and L-NAME, respectively, were also made into the functionally identified pressor region in the rostral VLM. RESULTS Microinjections of SNP into the rostral VLM pressor region produced a dose-dependent increase in mean arterial pressure and renal sympathetic nerve activity. At the highest dose of 50 nmol, the increase in MAP was 26 +/- 5 mmHg (P < 0.001) and the sympathetic nerve activity was 53 +/- 5% (P < 0.001). These effects were abolished following methylene blue injection into the same region. Injection of 10 nmol S-nitroso-glutathione also produced increases in MAP (15 +/- 2 mmHg, P < 0.001) and in renal sympathetic nerve activity (28 +/- 2%, P < 0.001). Microinjections of L- or D-arginine resulted in very small depressor responses, but had no significant effect on renal sympathetic nerve activity. Microinjections of L-NAME, but not of D-NAME, caused significant decreases in MAP (19 +/- 1 mmHg, P < 0.001) and in sympathetic nerve activity (30 +/- 3%, P < 0.001). CONCLUSIONS The results indicate that, in the anaesthetized rabbit with denervated baroreceptors, NO has a pressor and sympathoexcitatory action in the rostral VLM, which is mediated by a cyclic GMP-dependent mechanism. Second, endogenous NO may modulate sympathetic activity tonically, by a direct or indirect action on sympathoexcitatory neurons within the rostral VLM.
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Affiliation(s)
- Y Hirooka
- Department of Physiology, University of Sydney, N.S.W., Australia
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Polson JW, Potts PD, Li YW, Dampney RA. Fos expression in neurons projecting to the pressor region in the rostral ventrolateral medulla after sustained hypertension in conscious rabbits. Neuroscience 1995; 67:107-23. [PMID: 7477892 DOI: 10.1016/0306-4522(95)00034-g] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Previous studies in anaesthetized animals have shown that the baroreflex control of sympathetic vasomotor activity is mediated to a large extent by inhibitory inputs to sympathoexcitatory pressor neurons in the rostral part of the ventrolateral medulla. The aim of this study was to determine, in conscious rabbits, the distribution of neurons within the brain that have two properties characteristic of interneurons conveying baroreceptor signals to the rostral ventrolateral medulla: (i) they are activated by an increase in arterial pressure; and (ii) they project specifically to the rostral ventrolateral medulla pressor region. In a preliminary operation, an injection of the retrogradely transported tracer, fluorescent-labelled microspheres, was made into the physiologically identified pressor region in the rostral ventrolateral medulla. After a waiting period of one to eight weeks, hypertension was produced in the conscious rabbit by continuous intravenous infusion of phenylephrine at a rate sufficient to increase arterial pressure by approximately 20 mmHg, maintained for a period of 60 min. A control group of animals was infused with the vehicle solution alone. In confirmation of our previous study, hypertension produced by phenylephrine resulted in the neuronal expression of Fos (a marker of neuronal activation) in the nucleus of the solitary tract, area postrema, the intermediate and caudal parts of the ventrolateral medulla parabrachial complex, and in the central nucleus of the amygdala. Approximately 50% of the Fos-immunoreactive neurons in both the caudal and intermediate parts of the ventrolateral medulla were also retrogradely labelled from the rostral ventrolateral medulla pressor region; such double-labelled neurons were confined to a discrete longitudinal column located just ventrolateral to the nucleus ambiguus. Significant numbers of double-labelled neurons were also found in the nucleus of the solitary tract and area postrema, although these represented a much lower proportion (13-16%) of the total number of Fos-immunoreactive neurons in these regions. In the parabrachial complex, Fos-immunoreactive and retrogradely labelled neurons were largely separate populations, while in the amygdala they were entirely separate populations. In the control group of rabbits, virtually no double-labelled neurons were found in any of these regions. The results indicate that putative baroreceptor interneurons that project to the pressor region of the rostral ventrolateral medulla are virtually confined to the lower brainstem. In particular, they support the results of previous studies in anaesthetized animals indicating that neurons in the intermediate and caudal ventrolateral medulla convey baroreceptor signals to the rostral ventrolateral medulla pressor region, and extend them by demonstrating the precise anatomical distribution of these neurons.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- J W Polson
- Department of Physiology, University of Sydney, NSW, Australia
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Dampney RA, Li YW, Hirooka Y, Potts P, Polson JW. Use of c-fos functional mapping to identify the central baroreceptor reflex pathway: advantages and limitations. Clin Exp Hypertens 1995; 17:197-208. [PMID: 7735269 DOI: 10.3109/10641969509087065] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Prolonged stimulation of many neurons results in the expression of the immediate early gene c-fos, which in turn cause the production of the protein Fos, whose presence in a cell can be detected by immunocytochemistry. This method has been used in both conscious and anaesthetized animals to identify central neurons involved in the baroreceptor reflex. In this paper we review the factors that can influence c-fos expression, with particular emphasis on the effects of different anaesthetic agents. We conclude that the c-fos method of functional mapping, when applied carefully and critically, is a very useful method of identifying central neurons that are activated by cardiovascular stimuli in conscious animals. Anaesthetic agents can significantly alter c-fos expression, and this effect differs greatly according to the type of anaesthetic used.
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Affiliation(s)
- R A Dampney
- Department of Physiology, University of Sydney, NSW, Australia
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Hirooka Y, Polson JW, Dampney RA. Pressor response from rostral dorsomedial medulla is mediated by excitatory amino acid receptors in rostral VLM. Am J Physiol 1994; 267:R309-15. [PMID: 8048637 DOI: 10.1152/ajpregu.1994.267.1.r309] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Excitatory amino acid (EAA) receptors in the rostral part of the ventrolateral medulla (VLM) have been shown to mediate pressor responses elicited by stimulation of various peripheral afferent fibers as well as other central nuclei. This study tested the hypothesis that these receptors are a critical component in the central pathway mediating the powerful pressor response that is produced by stimulation of a group of neurons within a circumscribed region in the rostral dorsomedial medulla (RDM). In anesthetized rabbits, the pressor response elicited by unilateral microinjection of glutamate into this RDM region was measured before and after injection of kynurenic acid (Kyn), a broad-spectrum EAA receptor antagonist, into the physiologically identified pressor region of either the ipsilateral or contralateral rostral VLM. The pressor response to RDM stimulation was greatly reduced (to 24 +/- 4% of control) 5-10 min after injection of Kyn (but not the vehicle solution) into the ipsilateral rostral VLM; this response returned completely to its control value within 30-60 min after Kyn injection. By contrast, after Kyn injection into the contralateral rostral VLM, the pressor response to RDM stimulation was not affected (106 +/- 15% of control). The results indicate that the descending pressor pathway from the RDM to the spinal cord is mediated by EAA receptors in the rostral VLM pressor region. Furthermore, the pathway from the RDM to the rostral VLM is predominantly, if not exclusively, ipsilateral.
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Affiliation(s)
- Y Hirooka
- Department of Physiology, University of Sydney, New South Wales, Australia
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Siddall PJ, Polson JW, Dampney RA. Descending antinociceptive pathway from the rostral ventrolateral medulla: a correlative anatomical and physiological study. Brain Res 1994; 645:61-8. [PMID: 7914818 DOI: 10.1016/0006-8993(94)91638-1] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Microinjections of the excitatory amino acid L-glutamate were made into the rostral ventrolateral medulla (RVLM) of anesthetised cats, to map the sites at which selective stimulation of cell bodies elicited a significant antinociceptive response (> or = 15% inhibition of the increase in L7 ventral root activity reflexly evoked by stimulation of C-fiber afferents). Antinociceptive sites were largely confined to the RVLM subregion ventromedial to the retrofacial nucleus, extending from the caudal pole of the facial nucleus to the level approximately 2.5 mm more caudal. Increases in arterial pressure were also elicited from some sites in the RVLM, but these were mainly lateral to the antinociceptive sites. In a second series of experiments, rhodamine labeled microspheres or cholera toxin B-gold (CTB-gold) were injected into the dorsal horn of the L7 segment. In three of these experiments in which the injection sites were restricted to the dorsal horn, retrogradely labeled cells in the caudal pons and medulla were virtually all within either the nucleus raphe magnus or the RVLM. Furthermore, the labeled cells in the RVLM were virtually confined to a discrete group located just ventromedial to the retrofacial nucleus, i.e. within the antinociceptive region as mapped by glutamate microinjection. The results of the present study indicate that antinociceptive effects are elicited by stimulation of a subregion in the RVLM, which is located medial to the pressor region. Further, the antinociceptive effects may be mediated, at least in part, by cells projecting directly to the dorsal horn in the spinal cord.
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Affiliation(s)
- P J Siddall
- Department of Physiology, University of Sydney, NSW, Australia
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Polson JW, Halliday GM, McAllen RM, Coleman MJ, Dampney RA. Rostrocaudal differences in morphology and neurotransmitter content of cells in the subretrofacial vasomotor nucleus. J Auton Nerv Syst 1992; 38:117-37. [PMID: 1377728 DOI: 10.1016/0165-1838(92)90232-6] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The rostral ventrolateral medulla (RVLM) contains sympathoexcitatory neurons that exert a powerful control over the sympathetic outflow to the cardiovascular system. In the cat there is a concentration of such neurons (but not neurons subserving other functions) within a narrow longitudinal column in the RVLM termed the subretrofacial (SRF) nucleus. Furthermore, it has been suggested that there are subgroups of cells, located at different rostrocaudal levels of the SRF nucleus, that preferentially or exclusively control different vascular beds (e.g. in the kidney and hindlimb). The aim of this study was to map quantitatively the rostrocaudal distribution within the nucleus of different cell types, defined according to morphological and/or chemical criteria, and to correlate this with the regional vasomotor effects (in hindlimb and kidney) evoked by stimulation of SRF cells at the corresponding rostrocaudal levels. SRF cells were highly heterogeneous with respect to both their morphology and chemical properties. They varied greatly in size (equivalent diameter ranging from 10-40 microns) as well as in shape and orientation. An immunohistochemical examination using the avidin-biotin procedure revealed that many SRF cells (estimated 57% of all SRF cells) were immunoreactive for tyrosine hydroxylase (TH, a marker of catecholamine cells). In addition, there were SRF cells immunoreactive for neuropeptide Y (NPY, 11% of total), enkephalin (ENK, 16% of total), and serotonin (5HT, 10% of total), but not for substance P, galanin or somatostatin. Different cell types, defined according to their morphology and/or chemical properties, were unevenly distributed throughout the nucleus. In the most caudal part of the SRF nucleus, virtually all cells were TH-positive, and the large majority (estimated 80%) were NPY-positive, suggesting that many cells at this level contained both TH and NPY. In contrast, in the most rostral part of the SRF nucleus, only 30% of cells were TH-positive, and no NPY-positive cells were observed. Both 5HT- and ENK-positive cells were found throughout the rostrocaudal extent of the nucleus, but predominantly within its rostral part. Furthermore, TH-positive cells in the rostral SRF nucleus were on average significantly larger (mean equivalent diameter 18-43% greater) than TH/NPY-positive cells in the caudal part of the nucleus, but smaller than 5HT- or ENK-positive cells at the same level. Overall, rostral cells (regardless of their chemical type) were larger than caudal cells within the SRF nucleus (mean equivalent diameter 13-28% greater).(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- J W Polson
- Department of Physiology, University of Sydney, New South Wales, Australia
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Abstract
We examined the vasomotor and respiratory effects of angiotensin II microinjection into the rabbit ventrolateral medulla (VLM). Angiotensin II in the rostral and caudal VLM increased and decreased arterial pressure, respectively, but had no effect on phrenic nerve activity. In contrast, L-glutamate injections in the same areas altered both arterial pressure and phrenic nerve activity. The results suggest that angiotensin II may activate specifically vasomotor neurons but not respiratory neurons in the VLM.
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Affiliation(s)
- Y W Li
- Department of Physiology, University of Sydney, N.S.W., Australia
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