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Pedro JR, Moura LIF, Valério-Fernandes Â, Baptista FI, Gaspar JM, Pinheiro BS, Lemos C, Kaufmann FN, Morgado C, Silva-Santos CSD, Tavares I, Ferreira SG, Carvalho E, Ambrósio AF, Cunha RA, Duarte JMN, Köfalvi A. Transient gain of function of cannabinoid CB 1 receptors in the control of frontocortical glucose consumption in a rat model of Type-1 diabetes. Brain Res Bull 2020; 161:106-115. [PMID: 32428627 DOI: 10.1016/j.brainresbull.2020.05.004] [Citation(s) in RCA: 1] [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] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Revised: 04/23/2020] [Accepted: 05/04/2020] [Indexed: 12/31/2022]
Abstract
Here we aimed to unify some previous controversial reports on changes in both cannabinoid CB1 receptor (CB1R) expression and glucose metabolism in the forebrain of rodent models of diabetes. We determined how glucose metabolism and its modulation by CB1R ligands evolve in the frontal cortex of young adult male Wistar rats, in the first 8 weeks of streptozotocin-induced type-1 diabetes (T1D). We report that frontocortical CB1R protein density was biphasically altered in the first month of T1D, which was accompanied with a reduction of resting glucose uptake ex vivo in acute frontocortical slices that was normalized after eight weeks in T1D. This early reduction of glucose uptake in slices was also restored by ex vivo treatment with both the non-selective CB1R agonists, WIN55212-2 (500 nM) and the CB1R-selective agonist, ACEA (3 μM) while it was exacerbated by the CB1R-selective antagonist, O-2050 (500 nM). These results suggest a gain-of-function for the cerebrocortical CB1Rs in the control of glucose uptake in diabetes. Although insulin and IGF-1 receptor protein densities remained unaffected, phosphorylated GSKα and GSKβ levels showed different profiles 2 and 8 weeks after T1D induction in the frontal cortex. Altogether, the biphasic response in frontocortical CB1R density within a month after T1D induction resolves previous controversial reports on forebrain CB1R levels in T1D rodent models. Furthermore, this study also hints that cannabinoids may be useful to alleviate impaired glucoregulation in the diabetic cortex.
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Affiliation(s)
- Joana Reis Pedro
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Liane I F Moura
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Ângela Valério-Fernandes
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal; Institute for Interdisciplinary Research, University of Coimbra, 3030-789 Coimbra, Portugal
| | - Filipa I Baptista
- Coimbra Institute for Clinical and Biomedical Research, Faculty of Medicine, University of Coimbra, 3000-548 Coimbra, Portugal
| | - Joana M Gaspar
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Bárbara S Pinheiro
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Cristina Lemos
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal
| | | | - Carla Morgado
- Department of Biomedicine, Faculty of Medicine, University of Porto, Porto, Portugal
| | - Carla S da Silva-Santos
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Isaura Tavares
- Department of Biomedicine, Faculty of Medicine, University of Porto, Porto, Portugal; Instituto de Biologia Molecular e Celular, Universidade do Porto, Portugal; I3S Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Portugal
| | - Samira G Ferreira
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Eugénia Carvalho
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal; Institute for Interdisciplinary Research, University of Coimbra, 3030-789 Coimbra, Portugal; The Portuguese Diabetes Association (APDP), Lisbon, Portugal; Arkansas Children's Research Institute, and Department of Geriatrics, University of Arkansas for Medical Sciences, Arkansas 72205, United States
| | - António F Ambrósio
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal; Coimbra Institute for Clinical and Biomedical Research, Faculty of Medicine, University of Coimbra, 3000-548 Coimbra, Portugal; Association for Innovation and Biomedical Research on Light and Image (AIBILI), 3000-548 Coimbra, Portugal
| | - Rodrigo A Cunha
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal; Faculty of Medicine, University of Coimbra, 3004-504 Coimbra, Portugal
| | - João M N Duarte
- Department of Experimental Medical Science, Faculty of Medicine, Lund University, Lund, Sweden; Wallenberg Centre for Molecular Medicine, Lund University, Lund, Sweden
| | - Attila Köfalvi
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal; Institute for Interdisciplinary Research, University of Coimbra, 3030-789 Coimbra, Portugal.
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2
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Pinheiro BS, Lemos C, Neutzling Kaufmann F, Marques JM, da Silva-Santos CS, Carvalho E, Mackie K, Rodrigues RJ, Cunha RA, Köfalvi A. Hierarchical glucocorticoid-endocannabinoid interplay regulates the activation of the nucleus accumbens by insulin. Brain Res Bull 2016; 124:222-30. [PMID: 27208730 DOI: 10.1016/j.brainresbull.2016.05.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2015] [Revised: 05/16/2016] [Accepted: 05/17/2016] [Indexed: 12/28/2022]
Abstract
Here we asked if insulin activation of the nucleus accumbens in vitro is reflected by an increase in (3)H-deoxyglucose ([(3)H]DG) uptake, thus subserving a new model to study molecular mechanisms of central insulin actions. Additionally, we investigated the dependence of this insulin effect on endocannabinoids and corticosteroids, two major culprits in insulin resistance. We found that in acute accumbal slices, insulin (3 and 300nM but not at 0.3nM) produced an increase in [(3)H]DG uptake. The synthetic cannabinoid agonist, WIN55212-2 (500nM) and the glucocorticoid dexamethasone (10μM), impaired insulin (300nM) action on [(3)H]DG uptake. The glucocorticoid receptor (GcR) antagonist, mifepristone (10μM) prevented dexamethasone from inhibiting insulin's action. Strikingly, this anti-insulin action of dexamethasone was also blocked by two CB1 cannabinoid receptor (CB1R) antagonists, O-2050 (500nM) and SR141716A (500nM), as well as by tetrahydrolipstatin (10μM), an inhibitor of diacylglycerol lipases-the enzymes responsible for the synthesis of the endocannabinoid, 2-arachidonoyl-glycerol (2-AG). On the other hand, the blockade of the post-synaptic 2-AG metabolizing enzymes, α,β-serine hydrolase domain 6/12 by WWL70 (1μM) also prevented the action of insulin, probably via increasing endogenous 2-AG tone. Additionally, an anti-insulin receptor (InsR) antibody immunoprecipitated CB1Rs from accumbal homogenates, indicating a physical complexing of CB1Rs with InsRs that supports their functional interaction. Altogether, insulin stimulates glucose uptake in the nucleus accumbens. Accumbal GcR activation triggers the synthesis of 2-AG that in turn binds to the known CB1R-InsR heteromer, thus impeding insulin signaling.
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Affiliation(s)
- Bárbara S Pinheiro
- CNC, Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Cristina Lemos
- CNC, Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal
| | | | - Joana M Marques
- CNC, Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Carla S da Silva-Santos
- CNC, Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Eugénia Carvalho
- CNC, Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Ken Mackie
- Department of Psychological and Brain Sciences, Gill Center for Biomolecular Science, Indiana University, Bloomington, IN, USA
| | - Ricardo J Rodrigues
- CNC, Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal; Institute for Interdisciplinary Research, University of Coimbra, 3030-789 Coimbra, Portugal
| | - Rodrigo A Cunha
- CNC, Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal; FMUC, Faculty of Medicine, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Attila Köfalvi
- CNC, Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal; Institute for Interdisciplinary Research, University of Coimbra, 3030-789 Coimbra, Portugal.
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Köfalvi A, Lemos C, Martín-Moreno AM, Pinheiro BS, García-García L, Pozo MA, Valério-Fernandes Â, Beleza RO, Agostinho P, Rodrigues RJ, Pasquaré SJ, Cunha RA, de Ceballos ML. Stimulation of brain glucose uptake by cannabinoid CB2 receptors and its therapeutic potential in Alzheimer's disease. Neuropharmacology 2016; 110:519-529. [PMID: 26976670 DOI: 10.1016/j.neuropharm.2016.03.015] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [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: 06/20/2015] [Revised: 02/18/2016] [Accepted: 03/07/2016] [Indexed: 01/01/2023]
Abstract
Cannabinoid CB2 receptors (CB2Rs) are emerging as important therapeutic targets in brain disorders that typically involve neurometabolic alterations. We here addressed the possible role of CB2Rs in the regulation of glucose uptake in the mouse brain. To that aim, we have undertaken 1) measurement of (3)H-deoxyglucose uptake in cultured cortical astrocytes and neurons and in acute hippocampal slices; 2) real-time visualization of fluorescently labeled deoxyglucose uptake in superfused hippocampal slices; and 3) in vivo PET imaging of cerebral (18)F-fluorodeoxyglucose uptake. We now show that both selective (JWH133 and GP1a) as well as non-selective (WIN55212-2) CB2R agonists, but not the CB1R-selective agonist, ACEA, stimulate glucose uptake, in a manner that is sensitive to the CB2R-selective antagonist, AM630. Glucose uptake is stimulated in astrocytes and neurons in culture, in acute hippocampal slices, in different brain areas of young adult male C57Bl/6j and CD-1 mice, as well as in middle-aged C57Bl/6j mice. Among the endocannabinoid metabolizing enzymes, the selective inhibition of COX-2, rather than that of FAAH, MAGL or α,βDH6/12, also stimulates the uptake of glucose in hippocampal slices of middle-aged mice, an effect that was again prevented by AM630. However, we found the levels of the endocannabinoid, anandamide reduced in the hippocampus of TgAPP-2576 mice (a model of β-amyloidosis), and likely as a consequence, COX-2 inhibition failed to stimulate glucose uptake in these mice. Together, these results reveal a novel general glucoregulatory role for CB2Rs in the brain, raising therapeutic interest in CB2R agonists as nootropic agents.
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Affiliation(s)
- Attila Köfalvi
- CNC - Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal; Institute for Interdisciplinary Research, University of Coimbra, Coimbra, Portugal
| | - Cristina Lemos
- CNC - Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Ana M Martín-Moreno
- Neurodegeneration Group, Department of Cellular, Molecular and Developmental Neurobiology, Instituto Cajal, CSIC, Doctor Arce, 37, 28002 Madrid, Spain; CIBERNED; Centre for Biomedical Research on Neurodegenerative Diseases, Spain
| | - Bárbara S Pinheiro
- CNC - Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Luis García-García
- CAI de Cartografía Cerebral, Instituto Pluridisciplinar, UCM, Madrid, Spain
| | - Miguel A Pozo
- CAI de Cartografía Cerebral, Instituto Pluridisciplinar, UCM, Madrid, Spain; PET Technology Institute, Madrid, Spain
| | - Ângela Valério-Fernandes
- CNC - Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Rui O Beleza
- CNC - Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Paula Agostinho
- CNC - Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal; FMUC, Faculty of Medicine, University of Coimbra, Coimbra, Portugal
| | - Ricardo J Rodrigues
- CNC - Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal; Institute for Interdisciplinary Research, University of Coimbra, Coimbra, Portugal
| | - Susana J Pasquaré
- Neurodegeneration Group, Department of Cellular, Molecular and Developmental Neurobiology, Instituto Cajal, CSIC, Doctor Arce, 37, 28002 Madrid, Spain; Instituto de Investigaciones Bioquímicas de Bahía Blanca (INIBIBB), CONICET-Bahía Blanca and Universidad Nacional del Sur, Edificio E1, Camino La Carrindanga km 7, 8000 Bahía Blanca, Argentina
| | - Rodrigo A Cunha
- CNC - Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal; FMUC, Faculty of Medicine, University of Coimbra, Coimbra, Portugal
| | - María L de Ceballos
- Neurodegeneration Group, Department of Cellular, Molecular and Developmental Neurobiology, Instituto Cajal, CSIC, Doctor Arce, 37, 28002 Madrid, Spain; CIBERNED; Centre for Biomedical Research on Neurodegenerative Diseases, Spain.
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4
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Bitencourt RM, Alpár A, Cinquina V, Ferreira SG, Pinheiro BS, Lemos C, Ledent C, Takahashi RN, Sialana FJ, Lubec G, Cunha RA, Harkany T, Köfalvi A. Lack of presynaptic interaction between glucocorticoid and CB1 cannabinoid receptors in GABA- and glutamatergic terminals in the frontal cortex of laboratory rodents. Neurochem Int 2015. [PMID: 26196379 DOI: 10.1016/j.neuint.2015.07.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Corticosteroid and endocannabinoid actions converge on prefrontocortical circuits associated with neuropsychiatric illnesses. Corticosteroids can also modulate forebrain synapses by using endocannabinoid effector systems. Here, we determined whether corticosteroids can modulate transmitter release directly in the frontal cortex and, in doing so, whether they affect presynaptic CB1 cannabinoid receptor- (CB1R) mediated neuromodulation. By Western blotting of purified subcellular fractions of the rat frontal cortex, we found glucocorticoid receptors (GcRs) and CB1Rs enriched in isolated frontocortical nerve terminals (synaptosomes). CB1Rs were predominantly presynaptically located while GcRs showed preference for the post-synaptic fraction. Additional confocal microscopy analysis of cortical and hippocampal regions revealed vesicular GABA transporter-positive and vesicular glutamate transporter 1-positive nerve terminals endowed with CB1R immunoreactivity, apposing GcR-positive post-synaptic compartments. In functional transmitter release assay, corticosteroids, corticosterone (0.1-10 microM) and dexamethasone (0.1-10 microM) did not significantly affect the evoked release of [(3)H]GABA and [(14)C]glutamate in superfused synaptosomes, isolated from both rats and mice. In contrast, the synthetic cannabinoid, WIN55212-2 (1 microM) diminished the release of both [(3)H]GABA and [(14)C]glutamate, evoked with various depolarization paradigms. This effect of WIN55212-2 was abolished by the CB1R neutral antagonist, O-2050 (1 microM), and was absent in the CB1R KO mice. CB2R-selective agonists did not affect the release of either neurotransmitter. The lack of robust presynaptic neuromodulation by corticosteroids was unchanged upon either CB1R activation or genetic inactivation. Altogether, corticosteroids are unlikely to exert direct non-genomic presynaptic neuromodulation in the frontal cortex, but they may do so indirectly, via the stimulation of trans-synaptic endocannabinoid signaling.
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Affiliation(s)
- Rafael M Bitencourt
- CNC, Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal; Laboratory of Psychopharmacology, Dept. Pharmacology, Universidade Federal de Santa Catarina, Florianopolis 88049-900, Brazil
| | - Alán Alpár
- Division of Molecular Neurobiology, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-17177 Stockholm, Sweden
| | - Valentina Cinquina
- Department of Molecular Neurosciences, Center for Brain Research, Medical University of Vienna, A-1090 Vienna, Austria; University of Insubria, Via Ravasi, 2, 21100 Varese, Italy
| | - Samira G Ferreira
- CNC, Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal; FMUC, Faculty of Medicine, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Bárbara S Pinheiro
- CNC, Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Cristina Lemos
- CNC, Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal
| | | | - Reinaldo N Takahashi
- Laboratory of Psychopharmacology, Dept. Pharmacology, Universidade Federal de Santa Catarina, Florianopolis 88049-900, Brazil
| | - Fernando J Sialana
- Department of Pediatrics, Medical University of Vienna, Währinger Gürtel 18, A-1090 Vienna, Austria; CeMM Research Center for Molecular Medicine of the Austrian Academy of Science, Lazarettgasse 14, AKH BT 25.3, A-1090 Vienna, Austria
| | - Gert Lubec
- Department of Pediatrics, Medical University of Vienna, Währinger Gürtel 18, A-1090 Vienna, Austria
| | - Rodrigo A Cunha
- CNC, Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal; FMUC, Faculty of Medicine, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Tibor Harkany
- Division of Molecular Neurobiology, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-17177 Stockholm, Sweden; Department of Molecular Neurosciences, Center for Brain Research, Medical University of Vienna, A-1090 Vienna, Austria
| | - Attila Köfalvi
- CNC, Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal; Institute for Interdisciplinary Research, University of Coimbra, 3030-789 Coimbra, Portugal.
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5
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Köles L, Garção P, Zádori ZS, Ferreira SG, Pinheiro BS, da Silva-Santos CS, Ledent C, Köfalvi A. Presynaptic TRPV1 vanilloid receptor function is age- but not CB1 cannabinoid receptor-dependent in the rodent forebrain. Brain Res Bull 2013; 97:126-35. [PMID: 23831917 DOI: 10.1016/j.brainresbull.2013.06.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [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: 05/10/2012] [Revised: 06/14/2013] [Accepted: 06/27/2013] [Indexed: 02/01/2023]
Abstract
Neocortical and striatal TRPV1 (vanilloid or capsaicin) receptors (TRPV1Rs) are excitatory ligand-gated ion channels, and are implicated in psychiatric disorders. However, the purported presynaptic neuromodulator role of TRPV1Rs in glutamatergic, serotonergic or dopaminergic terminals of the rodent forebrain remains little understood. With the help of patch-clamp electrophysiology and neurochemical approaches, we mapped the age-dependence of presynaptic TRPV1R function, and furthermore, we aimed at exploring whether the presence of CB1 cannabinoid receptors (CB1Rs) influences the function of the TRPV1Rs, as both receptor types share endogenous ligands. We found that the major factor which affects presynaptic TRPV1R function is age: by post-natal day 13, the amplitude of capsaicin-induced release of dopamine and glutamate is halved in the rat striatum, and two weeks later, capsaicin already loses its effect. However, TRPV1R receptor function is not enhanced by chemical or genetic ablation of the CB1Rs in dopaminergic, glutamatergic and serotonergic terminals of the mouse brain. Altogether, our data indicate a possible neurodevelopmental role for presynaptic TRPV1Rs in the rodent brain, but we found no cross-talk between TRPV1Rs and CB1Rs in the same nerve terminal.
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Key Words
- 3Rs
- 4-AP
- 4-aminopyridine
- 7-, 14-, 29- and 60-day-old
- 7D, 14D, 29D, 60D
- ACEA
- ARC
- ARRIVE
- AUC
- American Radiolabeled Chemicals
- Animal Research: Reporting In Vivo Experiments
- BCA
- BSA
- CB(1) cannabinoid receptor
- CB(1)R
- DMSO
- DPM
- DTT
- Dopamine
- ECF
- EDTA
- EGTA
- FR%
- Federation for Laboratory Animal Science Associations
- Felasa
- GABA
- Glutamate
- HEPES
- KHR
- KO
- Krebs-HEPES-Ringer
- LiGTP
- MAO B
- MgATP
- N-(2-hydroxyethyl)piperazine-N′-(2-ethanesulfonic acid)
- N-arachidonyl dopamine
- NADA
- NO
- PMSF
- PVDF
- RTX
- SDS
- SEM
- Serotonin
- Striatum
- TBS-T
- TRPV(1) vanilloid receptor
- TRPV(1)R and TRPV(4)R
- Tris
- Tris-buffered saline with Tween 20
- WT
- aCSF
- arachidonyl-2′-chloroethylamide
- area-under-the-curve
- artificial cerebrospinal fluid
- bicinchoninic acid
- bovine serum albumin
- cannabinoid receptor type 1
- dimethyl sulfoxide
- disintegration per minute
- dithiothreitol
- enhanced chemi-fluorescence
- ethylene glycol-bis(2-aminoethylether)-N,N,N′,N′-tetraacetic acid
- ethylenediaminetetraacetic acid
- fractional release %
- knockout
- lithium guanozine triphosphate
- magnesium adenosine triphosphate
- monoamine oxidase B
- nitric oxide
- phenylmethanesulfonyl fluoride
- polyvinylidene difluoride
- replacement, reduction, refinement
- resiniferatoxin
- sEPSCs
- sodium dodecyl sulfate
- spontaneous excitatory postsynaptic currents
- standard error of the mean
- transient release potential receptor vanilloid type 4
- tris(hydroxymethyl)aminomethane
- wild-type
- γ-aminobutyric acid
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Affiliation(s)
- László Köles
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, Semmelweis University, Nagyvárad tér 4, 1089 Budapest, Hungary
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6
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Abstract
Accurate mechanical property data obtained at large shear deformations and high frequencies are a fundamental component of realistic numerical simulations of soft tissue injury. Although many commercial systems exist for testing shear properties of viscoelastic materials with properties similar to soft biological tissue, none are capable of determining properties at high loading rates necessary for modeling soft tissue injury. Previous custom shear testing systems, though capable of high-frequency loading, indirectly measure tissue properties by using analytical corrections for inertial effects. To address these limitations, a new custom designed oscillatory shear testing apparatus (STA) capable of testing soft biological tissues in simple shear has been constructed and validated. Through a proper selection of sample thickness, direct measurement of material properties at high frequencies is achieved mechanically without analytical inertial adjustments. The complex shear modulus of three mixtures of silicone gel with viscoelastic properties in a range similar to soft biological tissue was characterized in the STA over a dynamic frequency range of 20-200 Hz and validated with a commercially available solids rheometer. The frequency-dependent complex shear modulus measurements of the STA were within 10% of the rheometer measurements for all mixtures over the entire frequency range tested. The STA represents substantive improvement over current shear testing methods by providing direct measurement of the shear behavior of soft viscoelastic material at high frequencies. Mechanical property data gained from this device will provide a more realistic basis for numerical simulations of biological structures.
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Affiliation(s)
- K B Arbogast
- Department of Bioengineering, University of Pennsylvania, Philadelphia 19104-6392, USA
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