1
|
Patra PH, Tench B, Hitrec T, Holmes F, Drake R, Cerritelli S, Spanswick D, Pickering AE. Pro-Opiomelanocortin (POMC) neurons in the nucleus of the solitary tract mediate endorphinergic endogenous analgesia in mice. Pain 2022; 164:1051-1066. [PMID: 36448978 DOI: 10.1097/j.pain.0000000000002802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2021] [Accepted: 09/27/2022] [Indexed: 12/02/2022]
Abstract
ABSTRACT The nucleus of the solitary tract (NTS) contains pro-opiomelanocortin (POMC) neurons which are one of the two major sources of β-endorphin in the brain. The functional role of these NTS POMC neurons in nociceptive and cardiorespiratory function is debated. We have shown that NTS POMC optogenetic activation produces bradycardia and transient apnoea in a working heart brainstem preparation and chemogenetic activation with an engineered ion channel (PSAM) produced opioidergic analgesia in vivo . To better define the role of the NTS POMC neurons in behaving animals, we adopted in vivo optogenetics (ChrimsonR) and excitatory/inhibitory chemogenetic DREADD (hM3Dq/hM4Di) strategies in POMC-Cre mice. We show that optogenetic activation of NTS POMC neurons produces time-locked, graded, transient bradycardia and bradypnoea in anaesthetised mice which is naloxone sensitive (1 mg/kg, i.p) suggesting a role of β-endorphin. Both optogenetic and chemogenetic activation of NTS POMC neurons produces sustained thermal analgesia in behaving mice which can be blocked by naloxone. It also produced analgesia in inflammatory pain (carrageenan) but not in a neuropathic pain model (tibial nerve transection). Inhibiting NTS POMC neurons does not produce any effect on basal nociception but inhibits stress-induced analgesia (unlike inhibition of arcuate POMC neurons). Activation of NTS POMC neuronal populations in conscious mice did not cause respiratory depression, anxiety or locomotor deficit (in open field) nor affective preference. These findings indicate that NTS POMC neurons play a key role in the generation of endorphinergic endogenous analgesia and can also regulate cardiorespiratory function.
Collapse
Affiliation(s)
- Pabitra Hriday Patra
- Anaesthesia, Pain & Critical Care Research, School of Physiology, Pharmacology and Neuroscience, University of Bristol, BS8 1TD, UK
| | - Becks Tench
- Anaesthesia, Pain & Critical Care Research, School of Physiology, Pharmacology and Neuroscience, University of Bristol, BS8 1TD, UK
| | - Timna Hitrec
- Anaesthesia, Pain & Critical Care Research, School of Physiology, Pharmacology and Neuroscience, University of Bristol, BS8 1TD, UK
| | - Fiona Holmes
- Anaesthesia, Pain & Critical Care Research, School of Physiology, Pharmacology and Neuroscience, University of Bristol, BS8 1TD, UK
| | - Robert Drake
- Anaesthesia, Pain & Critical Care Research, School of Physiology, Pharmacology and Neuroscience, University of Bristol, BS8 1TD, UK
| | - Serena Cerritelli
- Radcliffe Department of Medicine, University of Oxford, John Radcliffe Hospital, Oxford, OX3 9DU, UK
| | - David Spanswick
- Neurosolutions, University of Warwick, Gibbet Hill Road, Coventry, West Midlands, CV4 7AL, UK
| | - Anthony Edward Pickering
- Anaesthesia, Pain & Critical Care Research, School of Physiology, Pharmacology and Neuroscience, University of Bristol, BS8 1TD, UK
| |
Collapse
|
2
|
Wall MJ, Hill E, Huckstepp R, Barkan K, Deganutti G, Leuenberger M, Preti B, Winfield I, Carvalho S, Suchankova A, Wei H, Safitri D, Huang X, Imlach W, La Mache C, Dean E, Hume C, Hayward S, Oliver J, Zhao FY, Spanswick D, Reynolds CA, Lochner M, Ladds G, Frenguelli BG. Selective activation of Gαob by an adenosine A 1 receptor agonist elicits analgesia without cardiorespiratory depression. Nat Commun 2022; 13:4150. [PMID: 35851064 PMCID: PMC9293909 DOI: 10.1038/s41467-022-31652-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Accepted: 06/23/2022] [Indexed: 02/06/2023] Open
Abstract
The development of therapeutic agonists for G protein-coupled receptors (GPCRs) is hampered by the propensity of GPCRs to couple to multiple intracellular signalling pathways. This promiscuous coupling leads to numerous downstream cellular effects, some of which are therapeutically undesirable. This is especially the case for adenosine A1 receptors (A1Rs) whose clinical potential is undermined by the sedation and cardiorespiratory depression caused by conventional agonists. We have discovered that the A1R-selective agonist, benzyloxy-cyclopentyladenosine (BnOCPA), is a potent and powerful analgesic but does not cause sedation, bradycardia, hypotension or respiratory depression. This unprecedented discrimination between native A1Rs arises from BnOCPA's unique and exquisitely selective activation of Gob among the six Gαi/o subtypes, and in the absence of β-arrestin recruitment. BnOCPA thus demonstrates a highly-specific Gα-selective activation of the native A1R, sheds new light on GPCR signalling, and reveals new possibilities for the development of novel therapeutics based on the far-reaching concept of selective Gα agonism.
Collapse
Affiliation(s)
- Mark J Wall
- School of Life Sciences, University of Warwick, Gibbet Hill Rd, Coventry, CV4 7AL, UK.
| | - Emily Hill
- School of Life Sciences, University of Warwick, Gibbet Hill Rd, Coventry, CV4 7AL, UK
| | - Robert Huckstepp
- School of Life Sciences, University of Warwick, Gibbet Hill Rd, Coventry, CV4 7AL, UK
| | - Kerry Barkan
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1PD, UK
| | - Giuseppe Deganutti
- Centre for Sport, Exercise and Life Sciences (CSELS), Faculty of Health and Life Sciences, Coventry University, Coventry, CV1 2DS, UK
- School of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, CO4 3SQ, UK
| | - Michele Leuenberger
- Institute of Biochemistry and Molecular Medicine, University of Bern, 3012, Bern, Switzerland
| | - Barbara Preti
- Institute of Biochemistry and Molecular Medicine, University of Bern, 3012, Bern, Switzerland
| | - Ian Winfield
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1PD, UK
| | - Sabrina Carvalho
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1PD, UK
| | - Anna Suchankova
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1PD, UK
| | | | - Dewi Safitri
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1PD, UK
- Pharmacology and Clinical Pharmacy Research Group, School of Pharmacy, Bandung Institute of Technology, Bandung, 40132, Indonesia
| | - Xianglin Huang
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1PD, UK
| | - Wendy Imlach
- Department of Physiology, Monash Biomedicine Discovery Institute, Monash University, Innovation Walk, Clayton, VIC, 3800, Australia
| | - Circe La Mache
- School of Life Sciences, University of Warwick, Gibbet Hill Rd, Coventry, CV4 7AL, UK
| | - Eve Dean
- School of Life Sciences, University of Warwick, Gibbet Hill Rd, Coventry, CV4 7AL, UK
| | - Cherise Hume
- School of Life Sciences, University of Warwick, Gibbet Hill Rd, Coventry, CV4 7AL, UK
| | - Stephanie Hayward
- School of Life Sciences, University of Warwick, Gibbet Hill Rd, Coventry, CV4 7AL, UK
| | - Jess Oliver
- School of Life Sciences, University of Warwick, Gibbet Hill Rd, Coventry, CV4 7AL, UK
| | | | - David Spanswick
- NeuroSolutions Ltd, Coventry, UK
- Department of Physiology, Monash Biomedicine Discovery Institute, Monash University, Innovation Walk, Clayton, VIC, 3800, Australia
- Warwick Medical School, University of Warwick, Gibbet Hill Rd, Coventry, CV4 7AL, UK
| | - Christopher A Reynolds
- Centre for Sport, Exercise and Life Sciences (CSELS), Faculty of Health and Life Sciences, Coventry University, Coventry, CV1 2DS, UK
- School of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, CO4 3SQ, UK
| | - Martin Lochner
- Institute of Biochemistry and Molecular Medicine, University of Bern, 3012, Bern, Switzerland
| | - Graham Ladds
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1PD, UK.
| | - Bruno G Frenguelli
- School of Life Sciences, University of Warwick, Gibbet Hill Rd, Coventry, CV4 7AL, UK.
| |
Collapse
|
3
|
Reichenbach A, Clarke RE, Stark R, Lockie SH, Mequinion M, Dempsey H, Rawlinson S, Reed F, Sepehrizadeh T, DeVeer M, Munder AC, Nunez-Iglesias J, Spanswick D, Mynatt R, Kravitz AV, Dayas CV, Brown R, Andrews ZB. Metabolic sensing in AgRP neurons integrates homeostatic state with dopamine signalling in the striatum. eLife 2022; 11:72668. [PMID: 35018884 PMCID: PMC8803314 DOI: 10.7554/elife.72668] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [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: 07/30/2021] [Accepted: 01/11/2022] [Indexed: 11/17/2022] Open
Abstract
Agouti-related peptide (AgRP) neurons increase motivation for food, however, whether metabolic sensing of homeostatic state in AgRP neurons potentiates motivation by interacting with dopamine reward systems is unexplored. As a model of impaired metabolic-sensing, we used the AgRP-specific deletion of carnitine acetyltransferase (Crat) in mice. We hypothesised that metabolic sensing in AgRP neurons is required to increase motivation for food reward by modulating accumbal or striatal dopamine release. Studies confirmed that Crat deletion in AgRP neurons (KO) impaired ex vivo glucose-sensing, as well as in vivo responses to peripheral glucose injection or repeated palatable food presentation and consumption. Impaired metabolic-sensing in AgRP neurons reduced acute dopamine release (seconds) to palatable food consumption and during operant responding, as assessed by GRAB-DA photometry in the nucleus accumbens, but not the dorsal striatum. Impaired metabolic-sensing in AgRP neurons suppressed radiolabelled 18F-fDOPA accumulation after ~30 min in the dorsal striatum but not the nucleus accumbens. Impaired metabolic sensing in AgRP neurons suppressed motivated operant responding for sucrose rewards during fasting. Thus, metabolic-sensing in AgRP neurons is required for the appropriate temporal integration and transmission of homeostatic hunger-sensing to dopamine signalling in the striatum.
Collapse
Affiliation(s)
| | - Rachel E Clarke
- Department of Physiology, Monash University, Clayton, Australia
| | - Romana Stark
- Department of Physiology, Monash University, Clayton, Australia
| | - Sarah H Lockie
- Department of Physiology, Monash University, Clayton, Australia
| | | | - Harry Dempsey
- Department of Physiology, Monash University, Clayton, Australia
| | - Sasha Rawlinson
- Department of Physiology, Monash University, Clayton, Australia
| | - Felicia Reed
- Department of Physiology, Monash University, Clayton, Australia
| | - Tara Sepehrizadeh
- Monash Biomedical Imaging Facility, Monash University, Clayton, Australia
| | - Michael DeVeer
- Monash Biomedical Imaging Facility, Monash University, Clayton, Australia
| | - Astrid C Munder
- Department of Physiology, Monash University, Clayton, Australia
| | - Juan Nunez-Iglesias
- Department of Anatomy and Developmental Biology, Monash University, Clayton, Australia
| | - David Spanswick
- Department of Physiology, Monash University, Clayton, Australia
| | - Randall Mynatt
- Gene Nutrient Interactions Laboratory, Pennington Biomedical Research Center, Baton Rouge, United States
| | - Alexxai V Kravitz
- Departments of Psychiatry, Washington University in St. Louis, Saint Louis, United States
| | - Christopher V Dayas
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, Australia
| | - Robyn Brown
- Department of Biochemistry and Pharmacology, University of Melbourne, Parkville, Australia
| | - Zane B Andrews
- Department of Physiology, Monash University, Clayton, Australia
| |
Collapse
|
4
|
Sykes MJ, Kekesi OS, Wong YT, Zhao FY, Spanswick D, Imlach WL. Neuron-specific responses to acetylcholine within the spinal dorsal horn circuits of rodent and primate. Neuropharmacology 2021; 198:108755. [PMID: 34416268 DOI: 10.1016/j.neuropharm.2021.108755] [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] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Revised: 08/08/2021] [Accepted: 08/10/2021] [Indexed: 10/20/2022]
Abstract
Excitatory and inhibitory neurotransmission within the spinal dorsal horn is tightly controlled to regulate transmission of nociceptive signals to the brain. One aspect of this control is modulation of neuronal activity through cholinergic signaling. Nociceptive neurons in the dorsal horn express both nicotinic and muscarinic cholinergic receptors and activation of these receptors reduces pain in humans, while inhibition leads to nociceptive hypersensitivity. At a cellular level, acetylcholine (ACh) has diverse effects on excitability which is dependent on the receptor and neuronal subtypes involved. In the present study we sought to characterize the electrophysiological responses of specific subsets of lamina II interneurons from rat and marmoset spinal cord. Neurons were grouped by morphology and by action potential firing properties. Whole-cell voltage-clamp recordings from lamina II dorsal horn neurons of adult rats showed that bath applied acetylcholine increased, decreased or had no effect on spontaneous synaptic current activity in a cell-type specific manner. ACh modulated inhibitory synaptic activity in 80% of neurons, whereas excitatory synaptic activity was affected in less than 50% of neurons. In whole-cell current clamp recordings, brief somatic application of ACh induced cell-type specific responses in 79% of rat lamina II neurons, which included: depolarization and action potential firing, subthreshold membrane depolarization, biphasic responses characterized by transient depolarization followed by hyperpolarization and membrane hyperpolarization alone. Similar responses were seen in marmoset lamina II neurons and the properties of each neuron group were consistent across species. ACh-induced hyperpolarization was blocked by the muscarinic antagonist atropine and all forms of acetylcholine-induced depolarization were blocked by the nicotinic antagonist mecamylamine. The cholinergic system plays an important role in regulating nociception and this study contributes to our understanding of how circuit activity is controlled by ACh at a cellular level in primate and rodent spinal cord.
Collapse
Affiliation(s)
- Matthew J Sykes
- Department of Physiology, Monash University, Melbourne, VIC, 3800, Australia; Monash Biomedicine Discovery Institute, Melbourne, VIC, 3800, Australia
| | - Orsolya S Kekesi
- Department of Physiology, Monash University, Melbourne, VIC, 3800, Australia; Monash Biomedicine Discovery Institute, Melbourne, VIC, 3800, Australia
| | - Yan T Wong
- Department of Physiology, Monash University, Melbourne, VIC, 3800, Australia; Monash Biomedicine Discovery Institute, Melbourne, VIC, 3800, Australia; Department of Electrical and Computer Systems Engineering, Melbourne, VIC, 3800, Australia
| | - Fei-Yue Zhao
- NeuroSolutions Ltd, Coventry, CV4 7AL, United Kingdom
| | - David Spanswick
- Department of Physiology, Monash University, Melbourne, VIC, 3800, Australia; Monash Biomedicine Discovery Institute, Melbourne, VIC, 3800, Australia; University of Warwick, Warwick Medical School, Coventry, CV4 7AL, United Kingdom
| | - Wendy L Imlach
- Department of Physiology, Monash University, Melbourne, VIC, 3800, Australia; Monash Biomedicine Discovery Institute, Melbourne, VIC, 3800, Australia.
| |
Collapse
|
5
|
Belgi A, Burnley JV, MacRaild CA, Chhabra S, Elnahriry KA, Robinson SD, Gooding SG, Tae HS, Bartels P, Sadeghi M, Zhao FY, Wei H, Spanswick D, Adams DJ, Norton RS, Robinson AJ. Alkyne-Bridged α-Conotoxin Vc1.1 Potently Reverses Mechanical Allodynia in Neuropathic Pain Models. J Med Chem 2021; 64:3222-3233. [PMID: 33724033 DOI: 10.1021/acs.jmedchem.0c02151] [Citation(s) in RCA: 8] [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
Several Conus-derived venom peptides are promising lead compounds for the management of neuropathic pain, with α-conotoxins being of particular interest. Modification of the interlocked disulfide framework of α-conotoxin Vc1.1 has been achieved using on-resin alkyne metathesis. Although introduction of a metabolically stable alkyne motif significantly disrupts backbone topography, the structural modification generates a potent and selective GABAB receptor agonist that inhibits Cav2.2 channels and exhibits dose-dependent reversal of mechanical allodynia in a behavioral rat model of neuropathic pain. The findings herein support the hypothesis that analgesia can be achieved via activation of GABABRs expressed in dorsal root ganglion (DRG) sensory neurons.
Collapse
Affiliation(s)
- Alessia Belgi
- School of Chemistry, Monash University, Clayton, Victoria 3800, Australia
| | - James V Burnley
- School of Chemistry, Monash University, Clayton, Victoria 3800, Australia
| | - Christopher A MacRaild
- Medicinal Chemistry, Monash Institute of Pharmaceutical Science, Monash University, 381 Royal Parade, Parkville, Victoria 3052, Australia
| | - Sandeep Chhabra
- Medicinal Chemistry, Monash Institute of Pharmaceutical Science, Monash University, 381 Royal Parade, Parkville, Victoria 3052, Australia
| | - Khaled A Elnahriry
- Medicinal Chemistry, Monash Institute of Pharmaceutical Science, Monash University, 381 Royal Parade, Parkville, Victoria 3052, Australia
| | - Samuel D Robinson
- Medicinal Chemistry, Monash Institute of Pharmaceutical Science, Monash University, 381 Royal Parade, Parkville, Victoria 3052, Australia
| | - Simon G Gooding
- School of Chemistry, Monash University, Clayton, Victoria 3800, Australia
| | - Han-Shen Tae
- Illawarra Health & Medical Research Institute (IHMRI), University of Wollongong, Wollongong, New South Wales 2522, Australia
| | - Peter Bartels
- Illawarra Health & Medical Research Institute (IHMRI), University of Wollongong, Wollongong, New South Wales 2522, Australia
| | - Mahsa Sadeghi
- Illawarra Health & Medical Research Institute (IHMRI), University of Wollongong, Wollongong, New South Wales 2522, Australia
| | | | | | - David Spanswick
- NeuroSolutions Ltd., Coventry CV4 7AL, U.K
- Biomedicine Discovery Institute and the Department of Physiology, Monash University, Clayton, Victoria 3800, Australia
- Warwick Medical School, University of Warwick, Coventry CV4 7AL, U.K
| | - David J Adams
- Illawarra Health & Medical Research Institute (IHMRI), University of Wollongong, Wollongong, New South Wales 2522, Australia
| | - Raymond S Norton
- Medicinal Chemistry, Monash Institute of Pharmaceutical Science, Monash University, 381 Royal Parade, Parkville, Victoria 3052, Australia
- ARC Centre for Fragment-Based Design, Monash University, Parkville, Victoria 3052, Australia
| | - Andrea J Robinson
- School of Chemistry, Monash University, Clayton, Victoria 3800, Australia
| |
Collapse
|
6
|
Kennedy AC, Belgi A, Husselbee BW, Spanswick D, Norton RS, Robinson AJ. α-Conotoxin Peptidomimetics: Probing the Minimal Binding Motif for Effective Analgesia. Toxins (Basel) 2020; 12:E505. [PMID: 32781580 PMCID: PMC7472027 DOI: 10.3390/toxins12080505] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Revised: 07/29/2020] [Accepted: 08/03/2020] [Indexed: 12/18/2022] Open
Abstract
Several analgesic α-conotoxins have been isolated from marine cone snails. Structural modification of native peptides has provided potent and selective analogues for two of its known biological targets-nicotinic acetylcholine and γ-aminobutyric acid (GABA) G protein-coupled (GABAB) receptors. Both of these molecular targets are implicated in pain pathways. Despite their small size, an incomplete understanding of the structure-activity relationship of α-conotoxins at each of these targets has hampered the development of therapeutic leads. This review scrutinises the N-terminal domain of the α-conotoxin family of peptides, a region defined by an invariant disulfide bridge, a turn-inducing proline residue and multiple polar sidechain residues, and focusses on structural features that provide analgesia through inhibition of high-voltage-activated Ca2+ channels. Elucidating the bioactive conformation of this region of these peptides may hold the key to discovering potent drugs for the unmet management of debilitating chronic pain associated with a wide range of medical conditions.
Collapse
Affiliation(s)
- Adam C. Kennedy
- School of Chemistry, Monash University, Clayton, Victoria 3800, Australia; (A.C.K.); (A.B.); (B.W.H.)
| | - Alessia Belgi
- School of Chemistry, Monash University, Clayton, Victoria 3800, Australia; (A.C.K.); (A.B.); (B.W.H.)
| | - Benjamin W. Husselbee
- School of Chemistry, Monash University, Clayton, Victoria 3800, Australia; (A.C.K.); (A.B.); (B.W.H.)
| | - David Spanswick
- Biomedicine Discovery Institute and the Department of Physiology, Monash University, Victoria 3800, Australia;
- Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK
- NeuroSolutions Ltd., Coventry CV4 7AL, UK
| | - Raymond S. Norton
- Medicinal Chemistry, Monash Institute of Pharmaceutical Science, Monash University, 381 Royal Parade, Parkville, Victoria 3052, Australia;
- ARC Centre for Fragment-Based Design, Monash University, Parkville, Victoria 3052, Australia
| | - Andrea J. Robinson
- School of Chemistry, Monash University, Clayton, Victoria 3800, Australia; (A.C.K.); (A.B.); (B.W.H.)
| |
Collapse
|
7
|
Haynes VR, Michael NJ, van den Top M, Zhao FY, Brown RD, De Souza D, Dodd GT, Spanswick D, Watt MJ. A Neural basis for Octanoic acid regulation of energy balance. Mol Metab 2020; 34:54-71. [PMID: 32180560 PMCID: PMC7011014 DOI: 10.1016/j.molmet.2020.01.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Revised: 12/11/2019] [Accepted: 01/03/2020] [Indexed: 12/13/2022] Open
Abstract
Objectives Nutrient sensing by hypothalamic neurons is critical for the regulation of food intake and energy expenditure. We aimed to identify long- and medium-chain fatty acid species transported into the brain, their effects on energy balance, and the mechanisms by which they regulate activity of hypothalamic neurons. Methods Simultaneous blood and cerebrospinal fluid (CSF) sampling was undertaken in rats and metabolic analyses using radiolabeled fatty acid tracers were performed on mice. Electrophysiological recording techniques were used to investigate signaling mechanisms underlying fatty acid-induced changes in activity of pro-opiomelanocortin (POMC) neurons. Results Medium-chain fatty acid (MCFA) octanoic acid (C8:0), unlike long-chain fatty acids, was rapidly transported into the hypothalamus of mice and almost exclusively oxidized, causing rapid, transient reductions in food intake and increased energy expenditure. Octanoic acid differentially regulates the excitability of POMC neurons, activating these neurons directly via GPR40 and inducing inhibition via an indirect non-synaptic, purine, and adenosine receptor-dependent mechanism. Conclusions MCFA octanoic acid is a central signaling nutrient that targets POMC neurons via distinct direct and indirect signal transduction pathways to instigate changes in energy status. These results could explain the beneficial health effects that accompany MCFA consumption. Octanoic acid (C8:0) is rapidly transported from blood to the cerebrospinal fluid. Octanoic acid rapidly reduces food intake and increases energy expenditure. Octanoic acid targets POMC neurons through direct and indirect signaling pathways. Activation of POMC neurons occurs directly through GPR40. Inhibition occurs through a nonsynaptic, purine and adenosine receptor-dependent mechanism.
Collapse
Affiliation(s)
- Vanessa R Haynes
- Department of Physiology, Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Melbourne, 3010, VIC, Australia; Metabolic Disease, Obesity and Diabetes Program, Biomedicine Discovery Institute and the Department of Physiology, Monash University, Clayton, 3800, VIC, Australia
| | - Natalie J Michael
- Metabolic Disease, Obesity and Diabetes Program, Biomedicine Discovery Institute and the Department of Physiology, Monash University, Clayton, 3800, VIC, Australia; Center for Hypothalamic Research, Department of Internal Medicine, UT Southwestern Medical Center, Dallas, TX, 75390, USA
| | | | | | - Russell D Brown
- Metabolic Disease, Obesity and Diabetes Program, Biomedicine Discovery Institute and the Department of Physiology, Monash University, Clayton, 3800, VIC, Australia
| | - David De Souza
- Metabolomics Australia, Bio21 Institute, University of Melbourne, Parkville, 3010, VIC, Australia
| | - Garron T Dodd
- Department of Physiology, Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Melbourne, 3010, VIC, Australia
| | - David Spanswick
- Metabolic Disease, Obesity and Diabetes Program, Biomedicine Discovery Institute and the Department of Physiology, Monash University, Clayton, 3800, VIC, Australia; Warwick Medical School, University of Warwick, Coventry, CV4 7AL, UK; NeuroSolutions Ltd, Coventry, UK.
| | - Matthew J Watt
- Department of Physiology, Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Melbourne, 3010, VIC, Australia.
| |
Collapse
|
8
|
Lee D, Lee KY, Bradley K, Spanswick D. Electrical activity evoked by 10 kHz spinal cord stimulation on superficial dorsal horn neurons in neuropathic pain rats. IBRO Rep 2019. [DOI: 10.1016/j.ibror.2019.07.1313] [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: 12/01/2022] Open
|
9
|
Dodd GT, Michael NJ, Lee-Young RS, Mangiafico SP, Pryor JT, Munder AC, Simonds SE, Brüning JC, Zhang ZY, Cowley MA, Andrikopoulos S, Horvath TL, Spanswick D, Tiganis T. Insulin regulates POMC neuronal plasticity to control glucose metabolism. eLife 2018; 7:38704. [PMID: 30230471 PMCID: PMC6170188 DOI: 10.7554/elife.38704] [Citation(s) in RCA: 73] [Impact Index Per Article: 12.2] [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: 05/27/2018] [Accepted: 09/14/2018] [Indexed: 11/30/2022] Open
Abstract
Hypothalamic neurons respond to nutritional cues by altering gene expression and neuronal excitability. The mechanisms that control such adaptive processes remain unclear. Here we define populations of POMC neurons in mice that are activated or inhibited by insulin and thereby repress or inhibit hepatic glucose production (HGP). The proportion of POMC neurons activated by insulin was dependent on the regulation of insulin receptor signaling by the phosphatase TCPTP, which is increased by fasting, degraded after feeding and elevated in diet-induced obesity. TCPTP-deficiency enhanced insulin signaling and the proportion of POMC neurons activated by insulin to repress HGP. Elevated TCPTP in POMC neurons in obesity and/or after fasting repressed insulin signaling, the activation of POMC neurons by insulin and the insulin-induced and POMC-mediated repression of HGP. Our findings define a molecular mechanism for integrating POMC neural responses with feeding to control glucose metabolism.
Collapse
Affiliation(s)
- Garron T Dodd
- Metabolism, Diabetes and Obesity Program, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Australia.,Department of Biochemistry and Molecular Biology, Monash University, Victoria, Australia
| | - Natalie J Michael
- Metabolism, Diabetes and Obesity Program, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Australia.,Department of Physiology, Monash University, Victoria, Australia
| | - Robert S Lee-Young
- Metabolism, Diabetes and Obesity Program, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Australia.,Department of Biochemistry and Molecular Biology, Monash University, Victoria, Australia.,Monash Metabolic Phenotyping Facility, Monash University, Victoria, Australia
| | - Salvatore P Mangiafico
- Department of Medicine (Austin Hospital), The University of Melbourne, Melbourne, Australia
| | - Jack T Pryor
- Department of Physiology, Monash University, Victoria, Australia.,Warwick Medical School, University of Warwick, Coventry, United Kingdom
| | - Astrid C Munder
- Metabolism, Diabetes and Obesity Program, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Australia.,Department of Physiology, Monash University, Victoria, Australia
| | - Stephanie E Simonds
- Metabolism, Diabetes and Obesity Program, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Australia.,Department of Physiology, Monash University, Victoria, Australia
| | - Jens Claus Brüning
- Department of Neuronal Control of Metabolism, Max Planck Institute for Metabolism Research, Cologne, Germany.,Center for Endocrinology, Diabetes, and Preventive Medicine, University Hospital Cologne, Cologne, Germany.,Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases, University of Cologne, Cologne, Germany.,Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany.,National Center for Diabetes Research, Neuherberg, Germany
| | - Zhong-Yin Zhang
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, United States
| | - Michael A Cowley
- Metabolism, Diabetes and Obesity Program, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Australia.,Department of Physiology, Monash University, Victoria, Australia
| | - Sofianos Andrikopoulos
- Department of Medicine (Austin Hospital), The University of Melbourne, Melbourne, Australia
| | - Tamas L Horvath
- Program in Integrative Cell Signaling and Neurobiology of Metabolism, Department of Comparative Medicine, Yale University School of Medicine, New Haven, United States.,Department of Anatomy and Histology, University of Veterinary Medicine, Hungary, Europe
| | - David Spanswick
- Metabolism, Diabetes and Obesity Program, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Australia.,Department of Physiology, Monash University, Victoria, Australia.,Warwick Medical School, University of Warwick, Coventry, United Kingdom
| | - Tony Tiganis
- Metabolism, Diabetes and Obesity Program, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Australia.,Department of Biochemistry and Molecular Biology, Monash University, Victoria, Australia.,Monash Metabolic Phenotyping Facility, Monash University, Victoria, Australia
| |
Collapse
|
10
|
van den Top M, Zhao FY, Viriyapong R, Michael NJ, Munder AC, Pryor JT, Renaud LP, Spanswick D. The impact of ageing, fasting and high-fat diet on central and peripheral glucose tolerance and glucose-sensing neural networks in the arcuate nucleus. J Neuroendocrinol 2017; 29. [PMID: 28834571 DOI: 10.1111/jne.12528] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Revised: 08/01/2017] [Accepted: 08/17/2017] [Indexed: 12/14/2022]
Abstract
Obesity and ageing are risk factors for diabetes. In the present study, we investigated the effects of ageing, obesity and fasting on central and peripheral glucose tolerance and on glucose-sensing neuronal function in the arcuate nucleus of rats, with a view to providing insight into the central mechanisms regulating glucose homeostasis and how they change or are subject to dysfunction with ageing and obesity. We show that, following a glucose load, central glucose tolerance at the level of the cerebrospinal fluid (CSF) and plasma is significantly reduced in rats maintained on a high-fat diet (HFD). With ageing, up to 2 years, central glucose tolerance was impaired in an age-dependent manner, whereas peripheral glucose tolerance remained unaffected. Ageing-induced peripheral glucose intolerance was improved by a 24-hour fast, whereas central glucose tolerance was not corrected. Pre-wean, immature animals have elevated basal plasma glucose levels and a delayed increase in central glucose levels following peripheral glucose injection compared to mature animals. Electrophysiological recording techniques revealed an energy-status-dependent role for glucose-excited, inhibited and adapting neurones, along with glucose-induced changes in synaptic transmission. We conclude that ageing affects central glucose tolerance, whereas HFD profoundly affects central and peripheral glucose tolerance and, in addition, glucose-sensing neurones adapt function in an energy-status-dependent manner.
Collapse
Affiliation(s)
| | - F-Y Zhao
- NeuroSolutions Ltd, Coventry, UK
| | - R Viriyapong
- Warwick Medical School, University of Warwick, Coventry, UK
- MOAC DTC, University of Warwick, Coventry, UK
| | - N J Michael
- Metabolic Disease and Obesity Program, Biomedicine Discovery Institute, Monash University, Melbourne, VIC, Australia
- Department of Physiology, Monash University, Clayton, VIC, Australia
| | - A C Munder
- Metabolic Disease and Obesity Program, Biomedicine Discovery Institute, Monash University, Melbourne, VIC, Australia
- Department of Physiology, Monash University, Clayton, VIC, Australia
| | - J T Pryor
- Warwick Medical School, University of Warwick, Coventry, UK
- Metabolic Disease and Obesity Program, Biomedicine Discovery Institute, Monash University, Melbourne, VIC, Australia
- Department of Physiology, Monash University, Clayton, VIC, Australia
| | - L P Renaud
- Ottawa Hospital Research Institute, Ottawa Civic Hospital, Ottawa, ON, Canada
| | - D Spanswick
- NeuroSolutions Ltd, Coventry, UK
- Warwick Medical School, University of Warwick, Coventry, UK
- Metabolic Disease and Obesity Program, Biomedicine Discovery Institute, Monash University, Melbourne, VIC, Australia
- Department of Physiology, Monash University, Clayton, VIC, Australia
- Neuroscience Program, Biomedicine Discovery Institute, Monash University, Melbourne, VIC, Australia
| |
Collapse
|
11
|
Dodd GT, Andrews ZB, Simonds SE, Michael NJ, DeVeer M, Brüning JC, Spanswick D, Cowley MA, Tiganis T. A Hypothalamic Phosphatase Switch Coordinates Energy Expenditure with Feeding. Cell Metab 2017; 26:375-393.e7. [PMID: 28768176 DOI: 10.1016/j.cmet.2017.07.013] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [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: 12/05/2016] [Revised: 04/13/2017] [Accepted: 07/17/2017] [Indexed: 12/17/2022]
Abstract
Beige adipocytes can interconvert between white and brown-like states and switch between energy storage versus expenditure. Here we report that beige adipocyte plasticity is important for feeding-associated changes in energy expenditure and is coordinated by the hypothalamus and the phosphatase TCPTP. A fasting-induced and glucocorticoid-mediated induction of TCPTP, inhibited insulin signaling in AgRP/NPY neurons, repressed the browning of white fat and decreased energy expenditure. Conversely feeding reduced hypothalamic TCPTP, to increase AgRP/NPY neuronal insulin signaling, white adipose tissue browning and energy expenditure. The feeding-induced repression of hypothalamic TCPTP was defective in obesity. Mice lacking TCPTP in AgRP/NPY neurons were resistant to diet-induced obesity and had increased beige fat activity and energy expenditure. The deletion of hypothalamic TCPTP in obesity restored feeding-induced browning and increased energy expenditure to promote weight loss. Our studies define a hypothalamic switch that coordinates energy expenditure with feeding for the maintenance of energy balance.
Collapse
Affiliation(s)
- Garron T Dodd
- Metabolic Disease and Obesity Program, Biomedicine Discovery Institute, Monash University, Victoria 3800, Australia; Department of Biochemistry and Molecular Biology, Monash University, Victoria 3800, Australia
| | - Zane B Andrews
- Metabolic Disease and Obesity Program, Biomedicine Discovery Institute, Monash University, Victoria 3800, Australia; Department of Physiology, Monash University, Victoria 3800, Australia
| | - Stephanie E Simonds
- Metabolic Disease and Obesity Program, Biomedicine Discovery Institute, Monash University, Victoria 3800, Australia; Department of Physiology, Monash University, Victoria 3800, Australia
| | - Natalie J Michael
- Metabolic Disease and Obesity Program, Biomedicine Discovery Institute, Monash University, Victoria 3800, Australia; Department of Physiology, Monash University, Victoria 3800, Australia
| | - Michael DeVeer
- Monash Biomedical Imaging, Monash University, Victoria 3168, Australia
| | - Jens C Brüning
- Max Plank Institute for Metabolism Research, Department of Neuronal Control of Metabolism, Gleueler Str. 50, 50931 Cologne, Germany; Center for Endocrinology, Diabetes, and Preventive Medicine (CEDP), University Hospital Cologne, Kerpener Str. 26, 50924 Cologne, Germany; Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD) and Center of Molecular Medicine Cologne (CMMC), University of Cologne, Joseph-Stelzmann-Str. 26, 50931 Cologne, Germany; National Center for Diabetes Research (DZD), Ingolstädter Land Str. 1, 85764 Neuherberg, Germany
| | - David Spanswick
- Metabolic Disease and Obesity Program, Biomedicine Discovery Institute, Monash University, Victoria 3800, Australia; Department of Physiology, Monash University, Victoria 3800, Australia
| | - Michael A Cowley
- Metabolic Disease and Obesity Program, Biomedicine Discovery Institute, Monash University, Victoria 3800, Australia; Department of Physiology, Monash University, Victoria 3800, Australia
| | - Tony Tiganis
- Metabolic Disease and Obesity Program, Biomedicine Discovery Institute, Monash University, Victoria 3800, Australia; Department of Biochemistry and Molecular Biology, Monash University, Victoria 3800, Australia.
| |
Collapse
|
12
|
Michael NJ, Simonds SE, van den Top M, Cowley MA, Spanswick D. Mitochondrial uncoupling in the melanocortin system differentially regulates NPY and POMC neurons to promote weight-loss. Mol Metab 2017; 6:1103-1112. [PMID: 29031712 PMCID: PMC5641603 DOI: 10.1016/j.molmet.2017.07.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Revised: 06/29/2017] [Accepted: 07/05/2017] [Indexed: 12/13/2022] Open
Abstract
Objective The mitochondrial uncoupling agent 2,4-dinitrophenol (DNP), historically used as a treatment for obesity, is known to cross the blood-brain-barrier, but its effects on central neural circuits controlling body weight are largely unknown. As hypothalamic melanocortin neuropeptide Y/agouti-related protein (NPY/AgRP) and pro-opiomelanocortin (POMC) neurons represent key central regulators of food intake and energy expenditure we investigated the effects of DNP on these neurons, food intake and energy expenditure. Method C57BL/6 and melanocortin-4 receptor (MC4R) knock-out mice were administered DNP intracerebroventricularly (ICV) and the metabolic changes were characterized. The specific role of NPY and POMC neurons and the ionic mechanisms mediating the effects of uncoupling were examined with in vitro electrophysiology performed on NPY hrGFP or POMC eGFP mice. Results Here we show DNP-induced differential effects on melanocortin neurons including inhibiting orexigenic NPY and activating anorexigenic POMC neurons through independent ionic mechanisms coupled to mitochondrial function, consistent with an anorexigenic central effect. Central administration of DNP induced weight-loss, increased BAT thermogenesis and browning of white adipose tissue, and decreased food intake, effects that were absent in MC4R knock-out mice and blocked by the MC4R antagonist, AgRP. Conclusion These data show a novel central anti-obesity mechanism of action of DNP and highlight the potential for selective melanocortin mitochondrial uncoupling to target metabolic disorders. Mitochondrial uncoupling of the melanocortin system with DNP induced weight-loss. DNP inhibited NPY neurones via activation of ATP-sensitive potassium channels. DNP activated POMC neurones via block of inwardly rectifying potassium channels. Central DNP reduced food intake and increased WAT browning and BAT thermogenesis.
Collapse
Affiliation(s)
- Natalie Jane Michael
- Metabolic Disease and Obesity Program, Biomedicine Discovery Institute, Monash University, Australia(5).
| | - Stephanie Elise Simonds
- Metabolic Disease and Obesity Program, Biomedicine Discovery Institute, Monash University, Australia(5).
| | | | - Michael Alexander Cowley
- Metabolic Disease and Obesity Program, Biomedicine Discovery Institute, Monash University, Australia(5).
| | - David Spanswick
- Neuroscience Program, Biomedicine Discovery Institute, Monash University, Australia(5); Neurosolutions, Coventry, P.O. 3517, UK; Metabolic and Vascular Health, Warwick Medical School, University of Warwick, Coventry, CV4 7AL, UK.
| |
Collapse
|
13
|
Jones MG, Andreou AP, McMahon SB, Spanswick D. Pharmacology of reflex blinks in the rat: a novel model for headache research. J Headache Pain 2016; 17:96. [PMID: 27770405 PMCID: PMC5074984 DOI: 10.1186/s10194-016-0686-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Accepted: 09/29/2016] [Indexed: 11/10/2022] Open
Abstract
Background Migraineurs are highly sensitive to the nitric oxide donor glyceryl trinitrate which triggers attacks in many sufferers. In animal studies, glyceryl trinitrate increases neuronal activity in the trigeminovascular pathway and elevates neurotransmitter levels in the brainstem. Many migraineurs also display alterations in blink reflexes, known to involve brainstem circuits. We investigated the effect of GTN on evoked blinks in the anaesthetised rat to determine whether such reflexes may prove useful as the basis for a novel animal model to evaluate potential anti-migraine therapeutic agents. Method In anaesthetised rats the electromyogram associated with the reflex blink evoked by corneal airpuff was recorded. Rats were infused with glyceryl trinitrate, sumatriptan plus glyceryl trinitrate or vehicle control. Changes in the magnitude of the reflex blink-associated electromyogram following these treatments were measured. Results Glyceryl trinitrate potentiated the evoked reflex blink-associated EMG response from 2 h after infusion. That effect was abolished by simultaneous infusion of sumatriptan with glyceryl trinitrate. Conclusions These results show that simple skin surface measurements of evoked electromyographic activity in the rat can reliably detect the evoked blink reflex that can be potentiated by nitric oxide donors. This novel model may be an effective tool for evaluating putative anti-migraine therapeutic agents.
Collapse
Affiliation(s)
- M G Jones
- Neurorestoration Group, Wolfson Centre for Age-Related Disease, Kings College London, London, UK. .,Zenith NeuroTech, Wolfson Centre for Age-Related Disease, Kings College London, London, UK.
| | - A P Andreou
- Academic Headache Centre, Wolfson Centre for Age-Related Disease, Kings College London, London, UK.,London and Pain Management and Neuromodulation Centre, St Thomas's Hospital, London, UK
| | - S B McMahon
- Neurorestoration Group, Wolfson Centre for Age-Related Disease, Kings College London, London, UK
| | - D Spanswick
- Neurosolutions Ltd., University of Warwick, Coventry, UK
| |
Collapse
|
14
|
Andreetta F, Carboni L, Grafton G, Jeggo R, Whyment AD, van den Top M, Hoyer D, Spanswick D, Barnes NM. Hippocampal 5-HT7 receptors signal phosphorylation of the GluA1 subunit to facilitate AMPA receptor mediated-neurotransmission in vitro and in vivo. Br J Pharmacol 2016; 173:1438-51. [PMID: 26773257 PMCID: PMC4831309 DOI: 10.1111/bph.13432] [Citation(s) in RCA: 15] [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] [Received: 07/24/2015] [Revised: 12/21/2015] [Accepted: 01/12/2016] [Indexed: 12/25/2022] Open
Abstract
BACKGROUND AND PURPOSE The 5-HT7 receptor is a GPCR that is the target of a broad range of antidepressant and antipsychotic drugs. Various studies have demonstrated an ability of the 5-HT7 receptor to modulate glutamatergic neurotransmission and cognitive processes although the potential impact upon AMPA receptors has not been investigated directly. The purposes of the present study were to investigate a direct modulation of the GluA1 AMPA receptor subunit and determine how this might influence AMPA receptor function. EXPERIMENTAL APPROACH The influence of pharmacological manipulation of the 5-HT7 receptor system upon phosphorylation of GluA1 subunits was assessed by Western blotting of fractionated proteins from hippocampal neurones in culture (or proteins resident at the neurone surface) and the functional impact assessed by electrophysiological recordings in rat hippocampus in vitro and in vivo. KEY RESULTS 5-HT7 receptor activation increased cAMP and relative pCREB levels in cultures of rat hippocampal neurones along with an increase in phosphorylation (Ser845) of the GluA1 AMPA receptor subunit evident in whole neurone extracts and within the neurone surface compartment. Electrophysiological recordings in rat hippocampus demonstrated a 5-HT7 receptor-mediated increase in AMPA receptor-mediated neurotransmission in vitro and in vivo. CONCLUSIONS AND IMPLICATIONS The 5-HT7 receptor-mediated phosphorylation of the GluA1 AMPA receptor provides a molecular mechanism consistent with the 5-HT7 receptor-mediated increase in AMPA receptor-mediated neurotransmission.
Collapse
Affiliation(s)
- Filippo Andreetta
- Clinical and Experimental Medicine, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham, UK
- Neurosciences CEDD, GlaxoSmithKline Medicine Research Centre, Verona, Italy
| | - Lucia Carboni
- Neurosciences CEDD, GlaxoSmithKline Medicine Research Centre, Verona, Italy
| | - Gillian Grafton
- Clinical and Experimental Medicine, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham, UK
| | | | | | | | - Daniel Hoyer
- Department of Pharmacology and Therapeutics, School of Biomedical Sciences, Faculty of Medicine, Dentistry and Health Sciences, The University of Melbourne, Parkville, Vic., Australia
- The Florey Institute of Neuroscience and Mental Health, The University of Melbourne, 30 Royal Parade, Parkville, Victoria 3052, Australia
- Department of Chemical Physiology, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA 92037, USA
| | | | - Nicholas M Barnes
- Clinical and Experimental Medicine, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham, UK
- Department of Pharmacology and Therapeutics, School of Biomedical Sciences, Faculty of Medicine, Dentistry and Health Sciences, The University of Melbourne, Parkville, Vic., Australia
| |
Collapse
|
15
|
O'Hare E, Jeggo R, Kim EM, Barbour B, Walczak JS, Palmer P, Lyons T, Page D, Hanna D, Meara JR, Spanswick D, Guo JP, McGeer EG, McGeer PL, Hobson P. Lack of support for bexarotene as a treatment for Alzheimer's disease. Neuropharmacology 2015; 100:124-30. [PMID: 26025659 DOI: 10.1016/j.neuropharm.2015.04.020] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [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: 02/13/2015] [Accepted: 04/22/2015] [Indexed: 12/16/2022]
Abstract
Bexarotene has been reported to reduce brain amyloid-β (Aβ) levels and to improve cognitive function in transgenic mouse models of Alzheimer's disease (AD). Four groups failed to fully replicate the primary results but the original authors claimed overall support for the general conclusions. Because of its potential clinical importance, the current work studied the effects of bexarotene using two animal species and highly relevant paradigms. Rats were tested for the ability of bexarotene to prevent changes induced by an Aβ challenge in the form intracerebroventricular (i.c.v) administration of 7PA2 conditioned medium (7PA2 CM) which contains high levels of Aβ species. Bexarotene had no effect on the long-term potentiation of evoked extracellular field excitatory postsynaptic potentials induced by i.c.v. 7PA2 CM. It also had no effect following subcutaneous administration of 2, 5, 10 and 15 mg/kg on behavioral/cognitive impairment using an alternating-lever cyclic-ratio schedule of operant responding in the rat. The effects of bexarotene were further tested using the APPSwFILon, PSEN1*M146L*L286V transgenic mouse model of AD, starting at the time Aβ deposits first begin to develop. Mice were sacrificed after 48 days of exposure to 100 mg bexarotene per day. No significant difference between test and control mice was found using a water-maze test, and no significant difference in the number of Aβ deposits in cerebral cortex, using two different antibodies, was apparent. These results question the potential efficacy of bexarotene for AD treatment, even if instigated in the preclinical period prior to the onset of cognitive deficits reported for human AD. This article is part of the Special Issue entitled 'Synaptopathy--from Biology to Therapy'.
Collapse
Affiliation(s)
- Eugene O'Hare
- School of Psychology, Queen's University, University Road, Belfast BT7 1NN, Northern Ireland, UK.
| | - Ross Jeggo
- Neurosolutions Limited, P.O. Box 3517, Coventry CV4 7ZS, UK.
| | - Eun-Mee Kim
- School of Psychology, University of Ulster, Cromore Road, Coleraine BT52 1SA, UK.
| | - Bridgeen Barbour
- School of Psychology, Queen's University, University Road, Belfast BT7 1NN, Northern Ireland, UK.
| | | | - Philip Palmer
- School of Psychology, Queen's University, University Road, Belfast BT7 1NN, Northern Ireland, UK.
| | - Taylor Lyons
- School of Psychology, Queen's University, University Road, Belfast BT7 1NN, Northern Ireland, UK.
| | - Deaglan Page
- School of Psychology, Queen's University, University Road, Belfast BT7 1NN, Northern Ireland, UK.
| | - Donncha Hanna
- School of Psychology, Queen's University, University Road, Belfast BT7 1NN, Northern Ireland, UK.
| | - Jolyon R Meara
- Institute of Primary Care and Public Health, Cardiff University CF10 3XQ, UK.
| | - David Spanswick
- Neurosolutions Limited, P.O. Box 3517, Coventry CV4 7ZS, UK; Cerebrasol Limited, P.O. Box 63534, Montreal Quebec H3W1JO, Canada; Department of Physiology, Monash University, Clayton VIC 3800, Australia.
| | - Jian-Ping Guo
- Kinsmen Laboratory of Neurological Research, University of British Columbia, Vancouver V6T1Z3, BC, Canada
| | - Edith G McGeer
- Kinsmen Laboratory of Neurological Research, University of British Columbia, Vancouver V6T1Z3, BC, Canada
| | - Patrick L McGeer
- Kinsmen Laboratory of Neurological Research, University of British Columbia, Vancouver V6T1Z3, BC, Canada.
| | - Peter Hobson
- Institute of Primary Care and Public Health, Cardiff University CF10 3XQ, UK.
| |
Collapse
|
16
|
Hebeisen S, Pires N, Loureiro AI, Bonifácio MJ, Palma N, Whyment A, Spanswick D, Soares-da-Silva P. Eslicarbazepine and the enhancement of slow inactivation of voltage-gated sodium channels: a comparison with carbamazepine, oxcarbazepine and lacosamide. Neuropharmacology 2014; 89:122-35. [PMID: 25242737 DOI: 10.1016/j.neuropharm.2014.09.008] [Citation(s) in RCA: 92] [Impact Index Per Article: 9.2] [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: 05/06/2014] [Revised: 08/17/2014] [Accepted: 09/03/2014] [Indexed: 11/30/2022]
Abstract
This study aimed at evaluating the effects of eslicarbazepine, carbamazepine (CBZ), oxcarbazepine (OXC) and lacosamide (LCM) on the fast and slow inactivated states of voltage-gated sodium channels (VGSC). The anti-epileptiform activity was evaluated in mouse isolated hippocampal slices. The anticonvulsant effects were evaluated in MES and the 6-Hz psychomotor tests. The whole-cell patch-clamp technique was used to investigate the effects of eslicarbazepine, CBZ, OXC and LCM on sodium channels endogenously expressed in N1E-115 mouse neuroblastoma cells. CBZ and eslicarbazepine exhibit similar concentration dependent suppression of epileptiform activity in hippocampal slices. In N1E-115 mouse neuroblastoma cells, at a concentration of 250 μM, the voltage dependence of the fast inactivation was not influenced by eslicarbazepine, whereas LCM, CBZ and OXC shifted the V0.5 value (mV) by -4.8, -12.0 and -16.6, respectively. Eslicarbazepine- and LCM-treated fast-inactivated channels recovered similarly to control conditions, whereas CBZ- and OXC-treated channels required longer pulses to recover. CBZ, eslicarbazepine and LCM shifted the voltage dependence of the slow inactivation (V0.5, mV) by -4.6, -31.2 and -53.3, respectively. For eslicarbazepine, LCM, CBZ and OXC, the affinity to the slow inactivated state was 5.9, 10.4, 1.7 and 1.8 times higher than to the channels in the resting state, respectively. In conclusion, eslicarbazepine did not share with CBZ and OXC the ability to alter fast inactivation of VGSC. Both eslicarbazepine and LCM reduce VGSC availability through enhancement of slow inactivation, but LCM demonstrated higher interaction with VGSC in the resting state and with fast inactivation gating.
Collapse
Affiliation(s)
| | - Nuno Pires
- BIAL - Portela & C(a), S.A., S. Mamede do Coronado, Portugal
| | - Ana I Loureiro
- BIAL - Portela & C(a), S.A., S. Mamede do Coronado, Portugal
| | | | - Nuno Palma
- BIAL - Portela & C(a), S.A., S. Mamede do Coronado, Portugal
| | | | - David Spanswick
- Neurosolutions Ltd, Coventry CV4 7ZS, UK; Department of Physiology, Monash University, Victoria, Australia
| | - Patrício Soares-da-Silva
- BIAL - Portela & C(a), S.A., S. Mamede do Coronado, Portugal; Department of Pharmacology and Therapeutics, Faculty of Medicine, University of Porto, Portugal; MedInUP - Center for Drug Discovery and Innovative Medicines, University of Porto, Porto, Portugal.
| |
Collapse
|
17
|
Zhao FY, Jeggo R, Wei H, Whyment A, Fang X, Spanswick D. In vivo electrophysiological recording techniques for the study of neuropathic pain in rodent models. Curr Protoc Pharmacol 2014; 66:11.15.1-11.15.26. [PMID: 25181009 DOI: 10.1002/0471141755.ph1115s66] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Neuropathic pain develops following nerve injury, and is a chronic pain syndrome that can persist long after repair of a wound or removal of the neurological insult. This condition remains poorly treated, not least because of a lack of mechanism-based therapeutics. Clinically, neuropathic pain is characterized by three major symptoms: thermal or mechanical allodynia (pain sensation in response to previously non-noxious stimuli); hyperalgesia (enhanced pain sensation to noxious stimulation); and spontaneous, ongoing pain. These clinical symptoms can be modeled in rodent neuropathic pain models using behavioral and electrophysiological readouts. This unit describes techniques designed to record pathophysiological electrical activity associated with neuropathic pain at the level of the periphery, in single fibers of primary sensory neurons, and from wide dynamic range (WDR) neurons of the dorsal horn of the spinal cord. These techniques can be employed in both naïve animals and in animal models of neuropathy to investigate fundamental mechanisms contributing to the neuropathic pain state and the site, mode, and mechanism of action of putative analgesics.
Collapse
Affiliation(s)
- Fei-Yue Zhao
- NeuroSolutions Limited, Coventry, United Kingdom
| | - Ross Jeggo
- NeuroSolutions Limited, Coventry, United Kingdom
| | - Haifeng Wei
- NeuroSolutions Limited, Coventry, United Kingdom
| | | | - Xin Fang
- NeuroSolutions Limited, Coventry, United Kingdom
| | - David Spanswick
- NeuroSolutions Limited, Coventry, United Kingdom.,Department of Physiology, Monash University, Clayton, Victoria, Australia.,Warwick Medical School, University of Warwick, Coventry, United Kingdom
| |
Collapse
|
18
|
Parsons CG, Jeggo RD, Staniaszek L, Spanswick D, Rammes G. P4‐378: REVERSAL OF AB‐INDUCED DEFICITS IN LONG‐TERM POTENTIATION (LTP)
IN VITRO
AND
IN VIVO
BY MRZ‐99030. Alzheimers Dement 2014. [DOI: 10.1016/j.jalz.2014.07.147] [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: 11/29/2022]
|
19
|
Abstract
Understanding the physiology, pharmacology, and plasticity associated with synaptic function is a key goal of neuroscience research and is fundamental to identifying the processes involved in the development and manifestation of neurological disease. A diverse range of electrophysiological methodologies are used to study synaptic function. Described in this unit is a technique for recording electrical activity from a single component of the central nervous system that is used to investigate pre- and post-synaptic elements of synaptic function. A strength of this technique is that it can be used on live animals, although the effect of anesthesia must be taken into consideration when interpreting the results. This methodology can be employed not only in naïve animals for studying normal physiological synaptic function, but also in a variety of disease models, including transgenic animals, to examine dysfunctional synaptic plasticity associated with neurological pathologies.
Collapse
Affiliation(s)
- Ross Jeggo
- Neurosolutions Limited, University of Warwick Medical School, Coventry, United Kingdom
| | - Fei-Yue Zhao
- Neurosolutions Limited, University of Warwick Medical School, Coventry, United Kingdom
| | - David Spanswick
- The Institute For Genomic Research, Rockville, Maryland.,Department of Physiology, Monash University, Clayton, Victoria, Australia.,University of Warwick Medical School, Coventry, United Kingdom
| |
Collapse
|
20
|
O'Hare E, Scopes DI, Kim EM, Palmer P, Jones M, Whyment AD, Spanswick D, Amijee H, Nerou E, McMahon B, Treherne JM, Jeggo R. Orally bioavailable small molecule drug protects memory in Alzheimer's disease models. Neurobiol Aging 2013; 34:1116-25. [DOI: 10.1016/j.neurobiolaging.2012.10.016] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2012] [Revised: 09/21/2012] [Accepted: 10/19/2012] [Indexed: 12/19/2022]
|
21
|
Scopes DIC, O'Hare E, Jeggo R, Whyment AD, Spanswick D, Kim EM, Gannon J, Amijee H, Treherne JM. Aβ oligomer toxicity inhibitor protects memory in models of synaptic toxicity. Br J Pharmacol 2013; 167:383-92. [PMID: 22913627 DOI: 10.1111/j.1476-5381.2012.01973.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [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] Open
Abstract
BACKGROUND AND PURPOSE Amyloid-β (Aβ) aggregation into synaptotoxic, prefibrillar oligomers is a major pathogenic event underlying the neuropathology of Alzheimer's disease (AD). The pharmacological and neuroprotective properties of a novel Aβ aggregation inhibitor, SEN1269, were investigated on aggregation and cell viability and in test systems relevant to synaptic function and memory, using both synthetic Aβ(1-42) and cell-derived Aβ oligomers. EXPERIMENTAL APPROACH Surface plasmon resonance studies measured binding of SEN1269 to Aβ(1-42) . Thioflavin-T fluorescence and MTT assays were used to measure its ability to block Aβ(1-42) -induced aggregation and reduction in cell viability. In vitro and in vivo long-term potentiation (LTP) experiments measured the effect of SEN1269 on deficits induced by synthetic Aβ(1-42) and cell-derived Aβ oligomers. Following i.c.v. administration of the latter, a complex (alternating-lever cyclic ratio) schedule of operant responding measured effects on memory in freely moving rats. KEY RESULTS SEN1269 demonstrated direct binding to monomeric Aβ(1-42) , produced a concentration-related blockade of Aβ(1-42) aggregation and protected neuronal cell lines exposed to Aβ(1-42) . In vitro, SEN1269 alleviated deficits in hippocampal LTP induced by Aβ(1-42) and cell-derived Aβ oligomers. In vivo, SEN1269 reduced the deficits in LTP and memory induced by i.c.v. administration of cell-derived Aβ oligomers. CONCLUSIONS AND IMPLICATIONS SEN1269 protected cells exposed to Aβ(1-42) , displayed central activity with respect to reducing Aβ-induced neurotoxicity and was neuroprotective in electrophysiological and behavioural models of memory relevant to Aβ-induced neurodegeneration. It represents a promising lead for designing inhibitors of Aβ-mediated synaptic toxicity as potential neuroprotective agents for treating AD.
Collapse
Affiliation(s)
- D I C Scopes
- Senexis Limited, Babraham Research Campus, Cambridge, UK.
| | | | | | | | | | | | | | | | | |
Collapse
|
22
|
Amijee H, Bate C, Williams A, Virdee J, Jeggo R, Spanswick D, Scopes DIC, Treherne JM, Mazzitelli S, Chawner R, Eyers CE, Doig AJ. The N-methylated peptide SEN304 powerfully inhibits Aβ(1-42) toxicity by perturbing oligomer formation. Biochemistry 2012; 51:8338-52. [PMID: 23025847 DOI: 10.1021/bi300415v] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Oligomeric forms of β-amyloid (Aβ) have potent neurotoxic activity and are the primary cause of neuronal injury and cell death in Alzheimer's disease (AD). Compounds that perturb oligomer formation or structure may therefore be therapeutic for AD. We previously reported that d-[(chGly)-(Tyr)-(chGly)-(chGly)-(mLeu)]-NH(2) (SEN304) is able to inhibit Aβ aggregation and toxicity, shown primarily by thioflavin T fluorescence and MTT (Kokkoni, N. et al. (2006) N-Methylated peptide inhibitors of β-amyloid aggregation and toxicity. Optimisation of inhibitor structure. Biochemistry 45, 9906-9918). Here we extensively characterize how SEN304 affects Aβ(1-42) aggregation and toxicity, using biophysical assays (thioflavin T, circular dichroism, SDS-PAGE, size exclusion chromatography, surface plasmon resonance, traveling wave ion mobility mass spectrometry, electron microscopy, ELISA), toxicity assays in cell culture (MTT and lactate dehydrogenase in human SH-SHY5Y cells, mouse neuronal cell death and synaptophysin) and long-term potentiation in a rat hippocampal brain slice. These data, with dose response curves, show that SEN304 is a powerful inhibitor of Aβ(1-42) toxicity, particularly effective at preventing Aβ inhibition of long-term potentiation. It can bind directly to Aβ(1-42), delay β-sheet formation and promote aggregation of toxic oligomers into a nontoxic form, with a different morphology that cannot bind thioflavin T. SEN304 appears to work by inducing aggregation, and hence removal, of Aβ oligomers. It is therefore a promising lead compound for Alzheimer's disease.
Collapse
Affiliation(s)
- Hozefa Amijee
- Senexis Limited, Babraham Research Campus, Cambridge CB22 3AT, UK
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
23
|
O'Hare E, Spanswick D, Jeggo R, Virdee J, Kim E. P3‐033: Survival analysis of fixed consecutive number schedule responding in APP over‐expressing transgenic rats. Alzheimers Dement 2011. [DOI: 10.1016/j.jalz.2011.05.1472] [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: 11/26/2022]
Affiliation(s)
- Eugene O'Hare
- Queen's University BelfastNew YorkNew YorkUnited States
| | | | - Ross Jeggo
- NeuroSolutions LimitedCoventryUnited Kingdom
| | | | | |
Collapse
|
24
|
Whyment AD, Coderre E, Wilson JMM, Renaud LP, O'Hare E, Spanswick D. Electrophysiological, pharmacological and molecular profile of the transient outward rectifying conductance in rat sympathetic preganglionic neurons in vitro. Neuroscience 2011; 178:68-81. [PMID: 21211550 DOI: 10.1016/j.neuroscience.2010.12.061] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [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] [Received: 03/30/2010] [Revised: 12/27/2010] [Accepted: 12/30/2010] [Indexed: 01/13/2023]
Abstract
Transient outward rectifying conductances or A-like conductances in sympathetic preganglionic neurons (SPN) are prolonged, lasting for hundreds of milliseconds to seconds and are thought to play a key role in the regulation of SPN firing frequency. Here, a multidisciplinary electrophysiological, pharmacological and molecular single-cell rt-PCR approach was used to investigate the kinetics, pharmacological profile and putative K+ channel subunits underlying the transient outward rectifying conductance expressed in SPN. SPN expressed a 4-aminopyridine (4-AP) sensitive transient outward rectification with significantly longer decay kinetics than reported for many other central neurons. The conductance and corresponding current in voltage-clamp conditions was also sensitive to the Kv4.2 and Kv4.3 blocker phrixotoxin-2 (1-10 μM) and the blocker of rapidly inactivating Kv channels, pandinotoxin-Kα (50 nM). The conductance and corresponding current was only weakly sensitive to the Kv1 channel blocker tityustoxin-Kα and insensitive to dendrotoxin I (200 nM) and the Kv3.4 channel blocker BDS-II (1 μM). Single-cell RT-PCR revealed mRNA expression for the α-subunits Kv4.1 and Kv4.3 in the majority and Kv1.5 in less than half of SPN. mRNA for accessory β-subunits was detected for Kvβ2 in all SPN with differential expression of mRNA for KChIP1, Kvβ1 and Kvβ3 and the peptidase homologue DPP6. These data together suggest that the transient outwardly rectifying conductance in SPN is mediated by members of the Kv4 subfamily (Kv4.1 and Kv4.3) in association with the β-subunit Kvβ2. Differential expression of the accessory β subunits, which may act to modulate channel density and kinetics in SPN, may underlie the prolonged and variable time-course of this conductance in these neurons.
Collapse
Affiliation(s)
- A D Whyment
- Warwick Medical School, University of Warwick, Coventry, CV4 7AL, UK
| | | | | | | | | | | |
Collapse
|
25
|
O'Hare E, Elliott JJ, Hobson P, Spanswick D, Kim EM. Behavioural deterioration induced by intrahippocampal NAC61-95 injections and attenuation with ibuprofen. Behav Brain Res 2009; 208:274-7. [PMID: 19931572 DOI: 10.1016/j.bbr.2009.11.027] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2009] [Revised: 11/08/2009] [Accepted: 11/16/2009] [Indexed: 11/17/2022]
Abstract
Pre-aggregated non-amyloid component of alpha-synuclein, NAC(61-95), was injected bilaterally into the CA3 area of rat hippocampus and behaviour was assessed using an alternating-lever cyclic-ratio (ALCR) schedule of operant responding. Four groups of rats were used (n=6 per group), subgroups were treated orally with either ibuprofen (40mg/kg) or vehicle (10% sucrose) twice daily. Intrahippocampal injection of NAC(61-95) increased lever switching errors and numbers of activated astrocytes, and ibuprofen treatment alleviated these effects.
Collapse
Affiliation(s)
- Eugene O'Hare
- School of Psychology, Queen's University, University Road, Belfast, BT7 1NN, Northern Ireland, UK.
| | | | | | | | | |
Collapse
|
26
|
O'Hare E, Elliott JJ, Hobson P, O'Mara SM, Spanswick D, Kim EM. Bilateral intrahippocampal NAC61-95 effects on behavior and moderation with L-NAME treatment. Neurosci Res 2009; 66:213-8. [PMID: 19913060 DOI: 10.1016/j.neures.2009.11.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2009] [Revised: 10/07/2009] [Accepted: 11/06/2009] [Indexed: 11/19/2022]
Abstract
Residues 61-95 of the non-amyloid component (NAC(61-95)) domain of alpha-synuclein are responsible for the aggregation and neurotoxicity of this protein. This study evaluated the effect of N((omega))-nitro-l-arginine methyl ester (l-NAME), a nitric oxide synthase inhibitor, on the behavior of rats bilaterally injected into the CA3 area of the dorsal hippocampus with aggregated NAC(61-95). Twenty-four male Sprague-Dawley rats were trained to respond under an alternating-lever cyclic-ratio (ALCR) operant schedule. When responding was stable, 12 rats were injected bilaterally into the CA3 area of the hippocampus with aggregated NAC(61-95) (5muicro per side; concentration 10(-4)M), the remaining 12 rats were similarly injected with sterile water (SW), six of the NAC(61-95) injected rats and six of the SW injected rats were treated for 90 days post-injections with 0.05mg/ml l-NAME in drinking water available ad libitum. Treatment with l-NAME alleviated NAC(61-95)-induced behavioral deficits, indicated through the measurement of lever switching errors and incorrect lever perseverations under the ALCR schedule, and reduced the number of activated astrocytes proximal to the injection sites.
Collapse
Affiliation(s)
- Eugene O'Hare
- School of Psychology, Queen's University, University Road, Belfast BT71NN, Northern Ireland, United Kingdom.
| | | | | | | | | | | |
Collapse
|
27
|
Barrett P, van den Top M, Wilson D, Mercer JG, Song CK, Bartness TJ, Morgan PJ, Spanswick D. Short photoperiod-induced decrease of histamine H3 receptors facilitates activation of hypothalamic neurons in the Siberian hamster. Endocrinology 2009; 150:3655-63. [PMID: 19372203 PMCID: PMC5393275 DOI: 10.1210/en.2008-1620] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Nonhibernating seasonal mammals have adapted to temporal changes in food availability through behavioral and physiological mechanisms to store food and energy during times of predictable plenty and conserve energy during predicted shortage. Little is known, however, of the hypothalamic neuronal events that lead to a change in behavior or physiology. Here we show for the first time that a shift from long summer-like to short winter-like photoperiod, which induces physiological adaptation to winter in the Siberian hamster, including a body weight decrease of up to 30%, increases neuronal activity in the dorsomedial region of the arcuate nucleus (dmpARC) assessed by electrophysiological patch-clamping recording. Increased neuronal activity in short days is dependent on a photoperiod-driven down-regulation of H3 receptor expression and can be mimicked in long-day dmpARC neurons by the application of the H3 receptor antagonist, clobenproprit. Short-day activation of dmpARC neurons results in increased c-Fos expression. Tract tracing with the trans-synaptic retrograde tracer, pseudorabies virus, delivered into adipose tissue reveals a multisynaptic neuronal sympathetic outflow from dmpARC to white adipose tissue. These data strongly suggest that increased activity of dmpARC neurons, as a consequence of down-regulation of the histamine H3 receptor, contributes to the physiological adaptation of body weight regulation in seasonal photoperiod.
Collapse
Affiliation(s)
- P Barrett
- Rowett Institute of Nutrition and Health, University of Aberdeen, Aberdeen AB21 9SB, United Kingdom
| | | | | | | | | | | | | | | |
Collapse
|
28
|
Scopes DI, Amijee H, Nerou E, Treherne M, O'Hare E, Jeggo R, Whyment A, Spanswick D. P2‐358: SEN1269: A novel inhibitor of amyloid‐beta toxicity. Alzheimers Dement 2008. [DOI: 10.1016/j.jalz.2008.05.1436] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Affiliation(s)
| | | | | | | | | | - Ross Jeggo
- NeuroSolutions LimitedCoventryUnited Kingdom
| | | | | |
Collapse
|
29
|
Abstract
Diabetes is a common endocrine disorder, primarily characterised by elevated plasma glucose levels. The disease affects all age groups worldwide. Most patients suffer from Type 2 diabetes, which is mainly due to insulin resistance. It is thought that changes in insulin signalling pathways underlie the development of insulin resistance. This article aims to review recent studies that have elucidated the role of individual proteins in these insulin signalling pathways. These studies have been undertaken using two strategies, one employing mice carrying a global null mutation of particular gene-encoding proteins by the homologous recombination method and another strategy using mice with tissue-specific insulin receptor and/or GLUT4 knockout by the Cre-loxP system. The various phenotypes of these knockout mice, and the light they shed on the etiology of insulin resistance, are discussed. By advancing our understanding of the complex molecular mechanisms underlying insulin resistance, these knock-out models may help us to develop more effective treatments for Type 2 diabetes.
Collapse
|
30
|
Affiliation(s)
- Kevin Lee
- Neurology and GI CEDD, Neurology and Gastrointestinal Centre of Excellence for Drug Discovery, GlaxoSmithKline, New Frontiers Science Park, Harlow, UK.
| | | |
Collapse
|
31
|
van den Top M, Lyons DJ, Lee K, Coderre E, Renaud LP, Spanswick D. Pharmacological and molecular characterization of ATP-sensitive K(+) conductances in CART and NPY/AgRP expressing neurons of the hypothalamic arcuate nucleus. Neuroscience 2006; 144:815-24. [PMID: 17137725 DOI: 10.1016/j.neuroscience.2006.09.059] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2006] [Revised: 09/27/2006] [Accepted: 09/27/2006] [Indexed: 11/16/2022]
Abstract
The role of hypothalamic ATP-sensitive potassium channels in the maintenance of energy homeostasis has been extensively explored. However, how these channels are incorporated into the neuronal networks of the arcuate nucleus remains unclear. Whole-cell patch-clamp recordings from rat arcuate nucleus neurons in hypothalamic slice preparations revealed widespread expression of functional ATP-sensitive potassium channels within the nucleus. ATP-sensitive potassium channels were expressed in orexigenic neuropeptide Y/agouti-related protein (NPY/AgRP) and ghrelin-sensitive neurons and in anorexigenic cocaine-and-amphetamine regulated transcript (CART) neurons. In 70% of the arcuate nucleus neurons recorded, exposure to glucose-free bathing medium induced inhibition of electrical excitability, the response being characterized by membrane hyperpolarization, a reduction in neuronal input resistance and a reversal potential consistent with opening of potassium channels. These effects were reversible upon re-introduction of glucose to the bathing medium or upon exposure to the ATP-sensitive potassium channel blockers tolbutamide or glibenclamide. The potassium channel opener diazoxide, but not pinacidil, also induced a tolbutamide and glibenclamide-sensitive inhibition of electrical excitability. Single-cell reverse transcription-polymerase chain reaction revealed expression of mRNA for sulfonylurea receptor 1 but not sulfonylurea receptor 2 subunits of ATP-sensitive potassium channels. Thus, rat arcuate nucleus neurons, including those involved in functionally antagonistic orexigenic and anorexigenic pathways express functional ATP-sensitive potassium channels which include sulfonylurea receptor 1 subunits. These data indicate a crucial role for these ion channels in central sensing of metabolic and energy status. However, further studies are needed to clarify the differential roles of these channels, the organization of signaling pathways that regulate them and how they operate in functionally opposing cell types.
Collapse
Affiliation(s)
- M van den Top
- Division of Clinical Sciences, Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK
| | | | | | | | | | | |
Collapse
|
32
|
Whyment AD, Blanks AM, Lee K, Renaud LP, Spanswick D. Histamine Excites Neonatal Rat Sympathetic Preganglionic Neurons In Vitro Via Activation of H1 Receptors. J Neurophysiol 2006; 95:2492-500. [PMID: 16354729 DOI: 10.1152/jn.01135.2004] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [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: 11/22/2022] Open
Abstract
The role of histamine in regulating excitability of sympathetic preganglionic neurons (SPNs) and the expression of histamine receptor mRNA in SPNs was investigated using whole-cell patch-clamp electrophysiological recording techniques combined with single-cell reverse transcriptase polymerase chain reaction (RT-PCR) in transverse neonatal rat spinal cord slices. Bath application of histamine (100 μM) or the H1 receptor agonist histamine trifluoromethyl toluidide dimaleate (HTMT; 10 μM) induced membrane depolarization associated with a decrease in membrane conductance in the majority (70%) of SPNs tested, via activation of postsynaptic H1 receptors negatively coupled to one or more unidentified K+ conductances. Histamine and HTMT application also induced or increased the amplitude and/or frequency of membrane potential oscillations in electrotonically coupled SPNs. The H2 receptor agonist dimaprit (10 μM) or the H3 receptor agonist imetit (100 nM) were without significant effect on the membrane properties of SPNs. Histamine responses were sensitive to the H1 receptor antagonist triprolidine (10 μM) and the nonselective potassium channel blocker barium (1 mM) but were unaffected by the H2 receptor antagonist tiotidine (10 μM) and the H3 receptor antagonist, clobenpropit (5 μM). Single cell RT-PCR revealed mRNA expression for H1 receptors in 75% of SPNs tested, with no expression of mRNA for H2, H3, or H4 receptors. These data represent the first demonstration of H1 receptor expression in SPNs and suggest that histamine acts to regulate excitability of these neurons via a direct postsynaptic effect on H1 receptors.
Collapse
MESH Headings
- Action Potentials/drug effects
- Action Potentials/physiology
- Animals
- Animals, Newborn
- Autonomic Fibers, Preganglionic/chemistry
- Autonomic Fibers, Preganglionic/drug effects
- Autonomic Fibers, Preganglionic/physiology
- Barium/pharmacology
- Dimaprit/pharmacology
- Female
- Ganglia, Sympathetic/chemistry
- Ganglia, Sympathetic/drug effects
- Ganglia, Sympathetic/physiology
- Histamine/analogs & derivatives
- Histamine/pharmacology
- Histamine/physiology
- Histamine Agonists/pharmacology
- Histamine H1 Antagonists/pharmacology
- Imidazoles/pharmacology
- In Vitro Techniques
- Male
- Membrane Potentials/drug effects
- Membrane Potentials/physiology
- Neurons/chemistry
- Neurons/drug effects
- Neurons/physiology
- Patch-Clamp Techniques
- Potassium/physiology
- RNA, Messenger/analysis
- RNA, Messenger/genetics
- Rats
- Rats, Inbred WKY
- Receptors, Histamine H1/genetics
- Receptors, Histamine H1/physiology
- Receptors, Histamine H2/physiology
- Receptors, Histamine H3/physiology
- Reverse Transcriptase Polymerase Chain Reaction
- Thiourea/analogs & derivatives
- Thiourea/pharmacology
- Triprolidine/pharmacology
Collapse
Affiliation(s)
- Andrew D Whyment
- Warwick Medical School, University of Warwick, Coventry, CV4 7AL, United Kingdom
| | | | | | | | | |
Collapse
|
33
|
Abstract
The specific blockade of endocannabinoids at the level of the cannabinoid receptor 1 (CB (1) receptor) is a new therapeutic option to reduce body weight and manage cardiovascular risk. Although clinical trials are underway to document the safety and efficacy of this approach, much is still unknown about this endogenous system. Endocannabinoids and their receptors are expressed in the central nervous system as well as in the periphery and regulate the central neural circuits for food uptake and peripheral metabolic circuits. Within the context of food uptake, the stimulation of the CB (1) receptor with Delta (9)-tetrahydrocannabinol (Delta (9)-THC) enhances food consumption, while its blockade with receptor antagonists is an emerging relevant therapeutic means to reduce body weight. Rimonabant is the first of a new class of drugs that interferes with the endocannabinoid system by blocking the CB (1) receptor. In recent clinical studies, a substantial reduction in body weight and waist circumference was associated with an improvement of the cardiovascular risk profile. In particular, increased HDL cholesterol, decreased serum triglycerides and improved insulin sensitivity were observed. Further research will serve to establish the role of these compounds in cardiovascular risk management.
Collapse
Affiliation(s)
- P Bramlage
- Institute for Clinical Pharmacology, Technical University, Dresden, Germany
| | | | | | | | | |
Collapse
|
34
|
Abstract
Integration of peripheral and central anabolic and catabolic inputs within the hypothalamic arcuate nucleus (ARC) is believed to be central to the maintenance of energy balance. In order to perform this complex task, neurons in the ARC express receptors for all major humoral and central transmitters involved in the maintenance of energy homeostasis. The integration of these inputs occurs at the cellular and circuit level and the resulting electrical output forms the origins for the activation of feeding and energy balance-related networks. Here, we discuss the role that active intrinsic membrane conductances, K(ATP) channels and intracellular second messenger systems play in the integration of metabolic stimuli at the cellular level in the ARC. We conclude that the research into the integration of hunger and satiety signals in the ARC has made substantial progress in the last decade, but we are far from unraveling the complex neuronal networks involved in the maintenance of energy homeostasis. The diverse range of inputs, neuronal integrative properties, targets, output signals and how these signals relate to the physiological output provides us with a colossal challenge for years to come. However, to battle the current obesity epidemic, target-specific drugs need to be developed for which the knowledge of neuronal pathways involved in the maintenance of energy homeostasis will be crucial.
Collapse
Affiliation(s)
- M van den Top
- Division of Clinical Sciences, Warwick Medical School, The University of Warwick, Coventry CV4 7AL, UK.
| | | |
Collapse
|
35
|
Nicholson R, Dixon AK, Spanswick D, Lee K. Noradrenergic receptor mRNA expression in adult rat superficial dorsal horn and dorsal root ganglion neurons. Neurosci Lett 2005; 380:316-21. [PMID: 15862909 DOI: 10.1016/j.neulet.2005.01.079] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2004] [Revised: 01/04/2005] [Accepted: 01/21/2005] [Indexed: 10/25/2022]
Abstract
Noradrenaline (NAdr) has well documented analgesic actions at the level of the spinal cord. Released from bulbospinal projections onto superficial dorsal horn (SDH) neurons, NAdr modulates the excitability of these neurons through the activation of alpha1, alpha2 or beta adrenoceptors. This study utilised in situ hybridisation to determine the specific expression of adrenoceptors within adult rat lumbar SDH and dorsal root ganglion (DRG) neurons, and reports the presence of alpha1A, alpha1B, alpha2B, beta1 and beta2 adrenoceptor mRNA within SDH neurons, and the presence of alpha1A, alpha1B and alpha2C adrenoceptor mRNA within DRG neurons. The present study provides an insight into the modulation of sensory processing at the level of the spinal cord following adrenoceptor activation.
Collapse
Affiliation(s)
- R Nicholson
- Department of Biological Sciences, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK.
| | | | | | | |
Collapse
|
36
|
Spanswick D, Renaud LP. Angiotensin II induces calcium-dependent rhythmic activity in a subpopulation of rat hypothalamic median preoptic nucleus neurons. J Neurophysiol 2005; 93:1970-6. [PMID: 15774710 DOI: 10.1152/jn.00769.2004] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [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: 11/22/2022] Open
Abstract
Whole cell patch-clamp recordings revealed a subpopulation (16%, n = 18/112) of rat median preoptic nucleus (MnPO) neurons responded to bath-applied angiotensin II (Ang II; 100 nM to 5 microM; 30-90 s) with a prolonged TTX-resistant membrane depolarization and rhythmic bursting activity. At rest, cells characteristically displayed relatively low input resistance and negative resting potentials. Ang-II-induced responses featured increased input resistance, a reversal potential of -95 +/- 2 mV, an increase in action potential duration from 2.9 +/- 0.5 to 4.3 +/- 0.8 ms, and the appearance of a rebound excitation at the offset of membrane responses to hyperpolarizing current injection. The latter was sensitive to Ni2+ (0.5-1 mM; n = 5), insensitive to extracellular Cs+ (1 mM, n = 7), and intracellular QX-314 (4 mM, n = 5), consistent with activation of a T-type Ca2+ conductance. Coincident with the Ang-II-induced depolarization was the appearance of rhythmic depolarizing shifts at a frequency of 0.14 +/- 0.09 Hz with superimposed bursts of 4-22 action potentials interspersed with silent periods persisting for >1 h after washout. These TTX-resistant depolarizing shifts increased in amplitude and decreased in frequency with membrane hyperpolarization with activity ceasing beyond approximately -80 mV, and were abolished in low-Ca(2+)/high-Mg2+ bathing medium (n = 6), Co2+ (1 mM; n = 6), or Ni2+ (0.5-1 mM; n = 8). Thus in a subpopulation of MnPO neurons, Ang II induces "pacemaker-like" activity by reducing a K(+)-dependent leak conductance that contributes to resting membrane potential and promoting of Ca(2+)-dependent regenerative auto-excitation mediated, in part, by a T-type Ca2+ conductance.
Collapse
Affiliation(s)
- David Spanswick
- Neurosciences Program, Ottawa Health Research Institute and University of Ottawa, 725 Parkdale Ave., Ottawa, Ontario, Canada K1Y 4E9
| | | |
Collapse
|
37
|
Abstract
Derivatives of 3-guanidinopropionic acid, such as leptin, reduce body weight in obese, diabetic mice. We have assessed whether one of these analogues, BVT.12777 activates intracellular signalling pathways in the arcuate nucleus in a manner analogous to leptin and insulin. In addition, because these hormones have been shown to activate K(ATP) channels in a subset of arcuate neurones, we examined whether this channel is also a functional endpoint for BVT.12777 in the arcuate nucleus. BVT.12777 transiently increased phosphorylation of MAPK, STAT3, PKB and GSK3, in a manner identical to that observed for leptin and insulin. BVT.12777 also hyperpolarized glucose-responsive neurones by increasing the activity of K(ATP) channels. The increase in K(ATP) activity driven by BVT.12777 was PI3-kinase independent, unlike leptin and insulin activation of this channel, and could also be elicited in isolated patches. However, K(ATP) activity induced by BVT.12777 was dependent on actin filament dynamics, both in intact neurones and isolated patches. Thus, BVT.12777 modulates arcuate neurone K(ATP) activity by re-organization of the cytoskeleton, a mechanism that has also been ascribed to leptin and insulin. Consequently, BVT.12777 appears to act as a leptin and insulin mimetic with respect to at least some elements of arcuate neurone intracellular signalling and the activation of K(ATP) channels. Resistance to leptin and insulin, associated with obesity has, at least in part, been postulated to be due to aberrant intracellular signalling in arcuate neurones. The data presented here indicate that it may be possible to develop drugs, which by-pass up-stream signalling components associated with adiposity hormone resistance, such as PI3-kinase, but can still induce functional outputs from arcuate neurones by targeting downstream components of the leptin and insulin signalling cascades.
Collapse
Affiliation(s)
- S Mirshamsi
- Division of Pathology and Neuroscience, University of Dundee, Ninewells Hospital and Medical School, Dundee, UK
| | | | | | | |
Collapse
|
38
|
Abstract
The healthcare burden that the obesity epidemic now poses in highly significant, in part due to increased risk of secondary chronic diseases such as hypertension. A lack of physical activity and high fat diets are major factors contributing to this condition. However, increasingly apparent is the genetic predisposition of individuals and ethnic groups to obesity. Present treatment strategies are currently inadequate and unlikely to have a major effect on the future prevalence of obesity. To slow the obesity epidemic, the source needs to be tackled now through fundamental research into the mechanisms by which obesity is manifest, and education on the risks and how to prevent it. This article will describe current and emerging treatments for obesity and review the recent advances in research that may provide the antiobesity treatments of the future. Research into obesity has escalated at considerable pace, catalysed by the discovery of the obese gene product leptin. Leptin is secreted by adipose tissue and acts via specific receptors in the brain to engage central neural pathways involved in regulating energy homeostasis. Since this discovery, numerous significant advances have been made in our understanding of how the brain integrates and responds to central and peripheral signals involved in maintaining energy homeostasis, and how disruption of these signalling mechanisms can manifest as obesity. As a consequence of these findings, numerous potential sites for therapeutic intervention into this condition have and are materializing. The aim of this review is to highlight current treatment strategies for obesity, recent advances in our understanding of the central neural control of energy balance, and what the authors consider to be the most promising targets for the development of novel antiobesity drugs in the future. Thus, the review focuses on leptin, neuropeptide Y, melanocortin and ghrelin signalling at the level of the CNS, and strategies targeting the sympathetic innervation of fat cells at the periphery.
Collapse
Affiliation(s)
- David Spanswick
- Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, UK/NeuroSolutions Ltd, Warwick BioVentures, Coventry CV4 7AL, UK
| | | |
Collapse
|
39
|
Nicholson R, Spanswick D, Lee K. Nitric oxide inhibits NMDA currents in a subpopulation of substantia gelatinosa neurons of the adult rat spinal cord. Neurosci Lett 2004; 359:180-4. [PMID: 15050693 DOI: 10.1016/j.neulet.2004.01.057] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2003] [Revised: 01/26/2004] [Accepted: 01/26/2004] [Indexed: 11/22/2022]
Abstract
In the present study, the actions of nitric oxide (NO) on NMDA mediated excitatory neurotransmission in substantia gelatinosa (SG) neurons of the adult rat spinal cord were investigated. Bath application of the NO donor sodium-nitroso-N-acetylpenicillamine (SNAP) reversibly inhibited NMDA receptor mediated excitatory postsynaptic currents evoked by electrical stimulation of the dorsal root. These effects of SNAP were prevented by pre-incubation with the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (carboxy PTIO) or the guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-alpha]quinoxalin-1-one, and were mimicked by the membrane permeable cGMP analogue dibutyryl cGMP. Finally, these effects were shown to be mediated at a postsynaptic level using acutely applied exogenous NMDA. In conclusion, we demonstrate for the first time the inhibition of NMDA mediated excitatory neurotransmission by NO in spinal cord SG neurons, an action mediated at least in part via the activation of guanylate cyclase.
Collapse
Affiliation(s)
- Ruth Nicholson
- Department of Biological Sciences, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
| | | | | |
Collapse
|
40
|
van den Top M, Lee K, Whyment AD, Blanks AM, Spanswick D. Orexigen-sensitive NPY/AgRP pacemaker neurons in the hypothalamic arcuate nucleus. Nat Neurosci 2004; 7:493-4. [PMID: 15097991 DOI: 10.1038/nn1226] [Citation(s) in RCA: 318] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2003] [Accepted: 02/24/2004] [Indexed: 11/08/2022]
Abstract
The hypothalamic arcuate nucleus (ARC) integrates and responds to satiety and hunger signals and forms the origins of the central neural response to perturbations in energy balance. Here we show that rat ARC neurons containing neuropeptide Y (NPY) and agouti-related protein (AgRP), which are conditional pacemakers, are activated by orexigens and inhibited by the anorexigen leptin. We propose a neuron-specific signaling mechanism through which central and peripheral signals engage the central neural anabolic drive.
Collapse
Affiliation(s)
- Marco van den Top
- Department of Biological Sciences, Gibbet Hill Campus, University of Warwick, Coventry CV4 7AL, UK
| | | | | | | | | |
Collapse
|
41
|
Whyment AD, Wilson JMM, Renaud LP, Spanswick D. Activation and integration of bilateral GABA-mediated synaptic inputs in neonatal rat sympathetic preganglionic neurones in vitro. J Physiol 2004; 555:189-203. [PMID: 14673187 PMCID: PMC1664830 DOI: 10.1113/jphysiol.2003.055665] [Citation(s) in RCA: 10] [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] [Received: 09/23/2003] [Accepted: 12/09/2003] [Indexed: 01/05/2023] Open
Abstract
The role of GABA receptors in synaptic transmission to neonatal rat sympathetic preganglionic neurones (SPNs) was investigated utilizing whole-cell patch clamp recording techniques in longitudinal and transverse spinal cord slice preparations. In the presence of glutamate receptor antagonists (NBQX, 5 microm and D-APV, 10 microm), electrical stimulation of the ipsilateral or contralateral lateral funiculi (iLF and cLF, respectively) revealed monosynaptic inhibitory postsynaptic potentials (IPSPs) in 75% and 65% of SPNs, respectively. IPSPs were sensitive to bicuculline (10 microM) in all neurones tested and reversed polarity around -55 mV, the latter indicating mediation via chloride conductances. In three neurones IPSPs evoked by stimulation of the iLF (n = 1) or cLF (n = 2) were partly sensitive to strychnine (2 microM). The expression of postsynaptic GABA(A) and GABA(B) receptors were confirmed by the sensitivity of SPNs to agonists, GABA (2 mm), muscimol (10-100 microM) or baclofen (10-100 microM), in the presence of TTX, each of which produced membrane hyperpolarization in all SPNs tested. Muscimol-induced responses were sensitive to bicuculline (1-10 microM) and SR95531 (10 microM) and baclofen-induced responses were sensitive to 2-hydroxy-saclofen (100-200 microM) and CGP55845 (200 nM). The GABA(C) receptor agonist CACA (200 microM) was without significant effect on SPNs. These results suggest that SPNs possess postsynaptic GABA(A) and GABA(B) receptors and that subsets of SPNs receive bilateral GABAergic inputs which activate GABA(A) receptors, coupled to a chloride conductance. At resting or holding potentials close to threshold either single or bursts (10-100 Hz) of IPSPs gave rise to a rebound excitation and action potential firing at the termination of the burst. This effect was mimicked by injection of small (10-20 pA) rectangular-wave current pulses, which revealed a time-dependent, Cs(+)-sensitive inward rectification and rebound excitation at the termination of the response to current injection. Synaptic activation of a rebound excitation mediated by a time-dependent inward rectification expressed intrinsically by SPNs may provide a novel mechanism enabling SPNs to be entrained to rhythms driven from the brainstem or higher centres.
Collapse
Affiliation(s)
- Andrew D Whyment
- Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, UK
| | | | | | | |
Collapse
|
42
|
Abstract
Neuropathic pain, arising from nerve injury, results in a chronic and debilitating form of pain that in the past has been poorly diagnosed and treated. During the past few years, intensive research has resulted in major progress towards understanding the basic mechanisms that contribute to this condition, and the renewed possibility of safe and effective medicines. Indeed, the next few years should see the first fruits of this labour reaching the market place and, with them, the opportunity to assess whether the scientific advances achieved have resulted in significant clinical improvement. In this article, some of the key compounds that will lead this charge and the clinical results obtained so far are discussed.
Collapse
Affiliation(s)
- Tracey Dickinson
- Quintiles Limited, Department of Pharmacology, Research Avenue South, Edinburgh EH14 4AP, UK
| | | | | | | |
Collapse
|
43
|
van den Top M, Nolan MF, Lee K, Richardson PJ, Buijs RM, Davies CH, Spanswick D. Orexins induce increased excitability and synchronisation of rat sympathetic preganglionic neurones. J Physiol 2003; 549:809-21. [PMID: 12702746 PMCID: PMC2342973 DOI: 10.1113/jphysiol.2002.033290] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2002] [Accepted: 03/20/2003] [Indexed: 11/08/2022] Open
Abstract
The neuropeptides orexin A and B are synthesised by perifornical and lateral hypothalamic (LH) neurones and exert a profound influence on autonomic sympathetic processes. LH neurones project to spinal areas containing sympathetic preganglionic neurones (SPNs) and therefore may directly modulate sympathetic output. In the present study we examined the possibility that orexinergic inputs from the LH influence SPN activity. Orexin-positive neurones in the LH were labelled with pseudorabies virus injected into the liver of parasympathetically denervated animals and orexin fibres were found adjacent to the soma and dendrites of SPNs. Orexin A or B (10-1000 nM) directly and reversibly depolarised SPNs in spinal cord slices. The response to orexin A was significantly reduced in the presence of the orexin receptor 1 (OX1R) antagonist SB334867A at concentrations of 1-10 micro M. Single cell reverse transcriptase-polymerase chain reaction revealed expression of mRNA for both OX1R and OX2R in the majority of orexin-sensitive SPNs. The orexin-induced depolarisation involved activation of pertussis toxin-sensitive G-proteins and closure of a K+ conductance via a protein kinase A (PKA)-dependent pathway that did not require an increase in intracellular Ca2+. Orexins also induced biphasic subthreshold membrane potential oscillations and synchronised activity between pairs of electrically coupled SPNs. Coupling coefficients and estimated junctional conductances between SPNs were not altered indicating synchronisation is due to activation of previously silent coupled neurones rather than modulation of gap junctions. These findings are consistent with a direct excitation and synchronisation of SPNs by orexinergic neurones that in vivo could increase the frequency and coherence of sympathetic nerve discharges and mediate LH effects on sympathetic components of energy homeostasis and cardiovascular control.
Collapse
Affiliation(s)
- Marco van den Top
- Department of Biological Sciences, The University of Warwick, Coventry CV4 7AL, UK
| | | | | | | | | | | | | |
Collapse
|
44
|
Abstract
In the present study, we have used in situ hybridization to examine the distribution of serotonin (5-HT) receptors in rat dorsal root ganglion (DRG) neurons. Within DRG neurons, mRNAs for 5-HT1B, 5-HT1D, 5-HT2A, 5-HT2B, 5-HT3B and 5-HT4 receptors were readily detected in small (<25 microm), medium (25-45 microm) and large (>45 microm) diameter neurons. In contrast mRNAs for 5-HT1A, 5-HT1E, 5-HT2C, 5-HT5A, 5-HT5B, 5-HT6 and 5-HT7 receptors were undetectable in these neurons. The present study provides an insight into the molecular profile of 5-HT receptor subtypes in neurons responsible for modulating sensory information.
Collapse
Affiliation(s)
- R Nicholson
- Pfizer Global Research and Development, Cambridge University Forvie Site, Robinson Way, CB2 2QB, Cambridge, UK
| | | | | | | | | |
Collapse
|
45
|
Wilson JMM, Coderre E, Renaud LP, Spanswick D. Active and passive membrane properties of rat sympathetic preganglionic neurones innervating the adrenal medulla. J Physiol 2002; 545:945-60. [PMID: 12482898 PMCID: PMC2290734 DOI: 10.1113/jphysiol.2002.023390] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [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: 11/08/2022] Open
Abstract
The intravascular release of adrenal catecholamines is a fundamental homeostatic process mediated via thoracolumbar spinal sympathetic preganglionic neurones (AD-SPN). To understand mechanisms regulating their excitability, whole-cell patch-clamp recordings were obtained from 54 retrogradely labelled neonatal rat AD-SPN. Passive membrane properties included a mean resting membrane potential, input resistance and time constant of -62 +/- 6 mV, 410 +/- 241 MOmega and 104 +/- 53 ms, respectively. AD-SPN were homogeneous with respect to their active membrane properties. These active conductances included transient outward rectification, observed as a delayed return to rest at the offset of the membrane response to hyperpolarising current pulses, with two components: a fast 4-AP-sensitive component (A-type conductance), contributing to the after-hyperpolarisation (AHP) and spike repolarisation; a slower prolonged Ba(2+)-sensitive component (D-like conductance). All AD-SPN expressed a Ba(2+)-sensitive instantaneous inwardly rectifying conductance activated at membrane potentials more negative than around -80 mV. A potassium-mediated, voltage-dependent sustained outward rectification activated at membrane potentials between -35 and -15 mV featured an atypical pharmacology with a component blocked by quinine, reduced by low extracellular pH and arachidonic acid, but lacking sensitivity to Ba(2+), TEA and intracellular Cs(+). This quinine-sensitive outward rectification contributes to spike repolarisation. Following block of potassium conductances by Cs(+) loading, AD-SPN revealed the capability for autorhythmicity and burst firing, mediated by a T-type Ca(2+) conductance. These data suggest the output capability is dynamic and diverse, and that the range of intrinsic membrane conductances expressed endow AD-SPN with the ability to generate differential and complex patterns of activity. The diversity of intrinsic membrane properties expressed by AD-SPN may be key determinants of neurotransmitter release from SPN innervating the adrenal medulla. However, factors other than active membrane conductances of AD-SPN must ultimately regulate the differential ratio of noradrenaline (NA) versus adrenaline (A) release secreted in response to various physiological and environmental demands.
Collapse
Affiliation(s)
- Jennifer M M Wilson
- Neurosciences, Ottawa Health Research Institute, University of Ottawa, Ontario, Canada K1Y 4E9, UK
| | | | | | | |
Collapse
|
46
|
van den Top M, Buijs RM, Ruijter JM, Delagrange P, Spanswick D, Hermes ML. Melatonin generates an outward potassium current in rat suprachiasmatic nucleus neurones in vitro independent of their circadian rhythm. Neuroscience 2002; 107:99-108. [PMID: 11744250 DOI: 10.1016/s0306-4522(01)00346-3] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.0] [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: 12/15/2022]
Abstract
The present study investigated the membrane mechanisms underlying the inhibitory influence of melatonin on suprachiasmatic nucleus (SCN) neurones in a hypothalamic slice preparation. Perforated-patch recordings were performed to prevent the rapid rundown of spontaneous firing rate as observed during whole cell recordings and to preserve circadian rhythmicity in SCN neurones. In current-clamp mode melatonin (1 microM or 1 nM) application, in the presence of agents that block action potential generation and fast synaptic transmission, resulted in a membrane hyperpolarisation accompanied with a decrease in input resistance in the majority of SCN neurones (71-86%). The amplitude of the hyperpolarisation was not found to be significantly different between circadian time 5-12 and 14-21. In voltage-clamp mode melatonin (1 microM or 1 nM) induced an outward current accompanied with an increase in membrane conductance. The current was found to be mainly potassium driven with voltage kinetics resembling those of an open rectifying potassium conductance. Investigations into the signal transduction mechanism revealed melatonin-induced inhibition of SCN neurones to be sensitive to pertussis toxin but independent of intracellular cAMP levels and phospholipase C activity. The present study shows that melatonin, at night-time physiological concentrations, reduces the neuronal excitability of the majority of SCN neurones independent of the time of application in the circadian cycle. Thus in vivo melatonin may be important for circadian time-keeping by amplifying the circadian rhythm in SCN neurones, by lowering their sensitivity to phase-shifting stimuli occurring at night.
Collapse
Affiliation(s)
- M van den Top
- Netherlands Institute for Brain Research, Amsterdam, The Netherlands.
| | | | | | | | | | | |
Collapse
|
47
|
Abstract
An important contributor to the generation of epileptiform activity is the synchronization of burst firing in a group of neurons. The aim of this study was to investigate whether gap junctions are involved in this synchrony using an in vitro model of epileptiform activity. Hippocampal slices (400 microm) were prepared from female Sprague-Dawley rats (120-170 g). The perfusion of slices with a medium containing no added magnesium and 4-aminopyridine (50 microM) resulted in the generation of spontaneous bursts of population spikes of a fast frequency along with less frequent negative-going bursts. The frequency of the bursts produced was consistent over a 3h period. Carbenoxolone (100 microM), a gap junction blocker and mineralocorticoid agonist, perfused for 75 min, reduced the frequency of both types of spontaneous burst activity. Perfusion of spironolactone (1 microM), a mineralocorticosteroid antagonist, for 15 min prior to and during carbenoxolone perfusion did not alter the ability of carbenoxolone to depress the frequency of spontaneous activity. The incubation of hippocampal slices in carbenoxolone prior to recording increased the time taken for the spontaneous activity to start on change to the zero magnesium/4-aminopyridine medium and decreased the total number of spontaneous bursts over the first 60 min period. The ability of carbenoxolone to delay induction of epileptiform activity and reduce established epileptiform activity suggests that gap junctions contribute to the synchronization of neuronal firing in this model.
Collapse
Affiliation(s)
- F M Ross
- Department of Biomedical Sciences, University of Aberdeen, Institute of Medical Sciences, Foresterhill, AB25 2ZD, Aberdeen, UK
| | | | | | | |
Collapse
|
48
|
Trudeau VL, Spanswick D, Fraser EJ, Larivière K, Crump D, Chiu S, MacMillan M, Schulz RW. The role of amino acid neurotransmitters in the regulation of pituitary gonadotropin release in fish. Biochem Cell Biol 2001; 78:241-59. [PMID: 10949077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023] Open
Abstract
Both glutamate and gamma-aminobutyric acid (GABA) are involved in pituitary hormone release in fish. Glutamate serves 2 purposes, both as a neurotransmitter and as a precursor for GABA synthesis. Glutamate can be catabolized to GABA by the actions of 2 distinct but related enzymes, glutamate decarboxylase 65 (GAD65) and GAD67. They derive from 2 different genes that likely arose from an early gene duplication prior to the emergence of teleosts more than 400 million years ago. There is good evidence for the involvement of GABA in luteinizing hormone (LH) release in fish. The mechanism of GABA action to stimulate LH release appears to be a combination of effects on GnRH release, potentiation of gonadotropin hormone-releasing hormone (GnRH) action, and in some cases directly at the LH cell. These actions appear to be dependent on such factors as sex or sex steroid levels, and there may also be species differences. Nevertheless, the stimulatory effects of GABA on LH are present in at least 4 fish species. In contrast, convincing data for the inhibitory effects of GABA on LH release have only been observed in 1 fish species. The sites and mechanisms of action of amino acid neurotransmitters on LH release have yet to be fully characterized. Both 130N-methyl-D-aspartic acid (NMDA) and S-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) type glutamate receptors are likely to have important roles. We suggest that it is a receptor similar to the GABA(A) type which mediates the effects of GABA on LH release in fish, at least partially acting on the GnRH neuron, but likely directly acting at the gonadotroph as well. GABA may also be involved in regulating the release of other pituitary hormones in fish, namely follicle stimulating hormone (FSH = GTH-I), prolactin, and growth hormone. Based on the findings described in this review, a working model for the involvement of glutamate and GABA in the regulation of LH release in teleost fish is proposed.
Collapse
Affiliation(s)
- V L Trudeau
- Department of Biology, University of Ottawa, ON, Canada.
| | | | | | | | | | | | | | | |
Collapse
|
49
|
Spanswick D, Smith MA, Mirshamsi S, Routh VH, Ashford ML. Insulin activates ATP-sensitive K+ channels in hypothalamic neurons of lean, but not obese rats. Nat Neurosci 2000; 3:757-8. [PMID: 10903566 DOI: 10.1038/77660] [Citation(s) in RCA: 363] [Impact Index Per Article: 15.1] [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: 01/09/2023]
Abstract
Insulin and leptin receptors are present in hypothalamic regions that control energy homeostasis, and these hormones reduce food intake and body weight in lean, but not obese, Zucker rats. Here we demonstrate that insulin, like leptin, hyperpolarizes lean rat hypothalamic glucose-responsive (GR) neurons by opening KATP channels. These findings suggest hypothalamic K ATP channel function is crucial to physiological regulation of food intake and body weight.
Collapse
Affiliation(s)
- D Spanswick
- Department of Biomedical Sciences, University of Aberdeen, Aberdeen Centre for Energy Regulation and Obesity, Institute of Medical Sciences, Foresterhill, Aberdeen AB25 2ZD, UK
| | | | | | | | | |
Collapse
|
50
|
Trudeau VL, Spanswick D, Fraser EJ, Larivière K, Crump D, Chiu S, MacMillan M, Schulz RW. The role of amino acid neurotransmitters in the regulation of pituitary gonadotropin release in fish. Biochem Cell Biol 2000. [DOI: 10.1139/o99-075] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Both glutamate and γ-aminobutyric acid (GABA) are involved in pituitary hormone release in fish. Glutamate serves 2 purposes, both as a neurotransmitter and as a precursor for GABA synthesis. Glutamate can be catabolized to GABA by the actions of 2 distinct but related enzymes, glutamate decarboxylase 65 (GAD65) and GAD67. They derive from 2 different genes that likely arose from an early gene duplication prior to the emergence of teleosts more than 400 million years ago. There is good evidence for the involvement of GABA in luteinizing hormone (LH) release in fish. The mechanism of GABA action to stimulate LH release appears to be a combination of effects on GnRH release, potentiation of gonadotropin hormone-releasing hormone (GnRH) action, and in some cases directly at the LH cell. These actions appear to be dependent on such factors as sex or sex steroid levels, and there may also be species differences. Nevertheless, the stimulatory effects of GABA on LH are present in at least 4 fish species. In contrast, convincing data for the inhibitory effects of GABA on LH release have only been observed in 1 fish species. The sites and mechanisms of action of amino acid neurotransmitters on LH release have yet to be fully characterized. Both N-methyl-D-aspartic acid (NMDA) and S-α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) type glutamate receptors are likely to have important roles. We suggest that it is a receptor similar to the GABAA type which mediates the effects of GABA on LH release in fish, at least partially acting on the GnRH neuron, but likely directly acting at the gonadotroph as well. GABA may also be involved in regulating the release of other pituitary hormones in fish, namely follicle stimulating hormone (FSH = GTH-I), prolactin, and growth hormone. Based on the findings described in this review, a working model for the involvement of glutamate and GABA in the regulation of LH release in teleost fish is proposed. Key words: glutamate, GABA, luteinizing hormone, muscimol, patch clamp electrophysiology, reproduction, fish.
Collapse
|