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Achanta LB, Thomas DS, Housley GD, Rae CD. AMP-activated protein kinase activators have compound and concentration-specific effects on brain metabolism. J Neurochem 2024; 168:677-692. [PMID: 36977628 DOI: 10.1111/jnc.15815] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Revised: 03/18/2023] [Accepted: 03/20/2023] [Indexed: 03/30/2023]
Abstract
AMP-activated protein kinase (AMPK) is a key sensor of energy balance playing important roles in the balancing of anabolic and catabolic activities. The high energy demands of the brain and its limited capacity to store energy indicate that AMPK may play a significant role in brain metabolism. Here, we activated AMPK in guinea pig cortical tissue slices, both directly with A769662 and PF 06409577 and indirectly with AICAR and metformin. We studied the resultant metabolism of [1-13C]glucose and [1,2-13C]acetate using NMR spectroscopy. We found distinct activator concentration-dependent effects on metabolism, which ranged from decreased metabolic pool sizes at EC50 activator concentrations with no expected stimulation in glycolytic flux to increased aerobic glycolysis and decreased pyruvate metabolism with certain activators. Further, activation with direct versus indirect activators produced distinct metabolic outcomes at both low (EC50) and higher (EC50 × 10) concentrations. Specific direct activation of β1-containing AMPK isoforms with PF 06409577 resulted in increased Krebs cycle activity, restoring pyruvate metabolism while A769662 increased lactate and alanine production, as well as labelling of citrate and glutamine. These results reveal a complex metabolic response to AMPK activators in brain beyond increased aerobic glycolysis and indicate that further research is warranted into their concentration- and mechanism-dependent impact.
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Affiliation(s)
- Lavanya B Achanta
- Neuroscience Research Australia, Barker St, Randwick, New South Wales, 2031, Australia
- Translational Neuroscience Facility, School of Biomedical Sciences, UNSW, Sydney, New South Wales, 2052, Australia
| | - Donald S Thomas
- Mark Wainwright Analytical Centre, UNSW, Sydney, New South Wales, 2052, Australia
| | - Gary D Housley
- Translational Neuroscience Facility, School of Biomedical Sciences, UNSW, Sydney, New South Wales, 2052, Australia
| | - Caroline D Rae
- Neuroscience Research Australia, Barker St, Randwick, New South Wales, 2031, Australia
- School of Psychology, UNSW, Sydney, New South Wales, 2052, Australia
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2
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Hone-Blanchet A, Antal B, McMahon L, Lithen A, Smith NA, Stufflebeam S, Yen YF, Lin A, Jenkins BG, Mujica-Parodi LR, Ratai EM. Acute administration of ketone beta-hydroxybutyrate downregulates 7T proton magnetic resonance spectroscopy-derived levels of anterior and posterior cingulate GABA and glutamate in healthy adults. Neuropsychopharmacology 2023; 48:797-805. [PMID: 35995971 PMCID: PMC10066400 DOI: 10.1038/s41386-022-01364-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Revised: 06/08/2022] [Accepted: 06/10/2022] [Indexed: 11/08/2022]
Abstract
Glucose metabolism is impaired in brain aging and several neurological conditions. Beneficial effects of ketones have been reported in the context of protecting the aging brain, however, their neurophysiological effect is still largely uncharacterized, hurdling their development as a valid therapeutic option. In this report, we investigate the neurochemical effect of the acute administration of a ketone d-beta-hydroxybutyrate (D-βHB) monoester in fasting healthy participants with ultrahigh-field proton magnetic resonance spectroscopy (MRS). In two within-subject metabolic intervention experiments, 7 T MRS data were obtained in fasting healthy participants (1) in the anterior cingulate cortex pre- and post-administration of D-βHB (N = 16), and (2) in the posterior cingulate cortex pre- and post-administration of D-βHB compared to active control glucose (N = 26). Effect of age and blood levels of D-βHB and glucose were used to further explore the effect of D-βHB and glucose on MRS metabolites. Results show that levels of GABA and Glu were significantly reduced in the anterior and posterior cortices after administration of D-βHB. Importantly, the effect was specific to D-βHB and not observed after administration of glucose. The magnitude of the effect on GABA and Glu was significantly predicted by older age and by elevation of blood levels of D-βHB. Together, our results show that administration of ketones acutely impacts main inhibitory and excitatory transmitters in the whole fasting cortex, compared to normal energy substrate glucose. Critically, such effects have an increased magnitude in older age, suggesting an increased sensitivity to ketones with brain aging.
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Affiliation(s)
- Antoine Hone-Blanchet
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, 02129, USA
| | - Botond Antal
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, 02129, USA
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Liam McMahon
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Andrew Lithen
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Nathan A Smith
- Center for Neuroscience Research, Children's National Research Institute, Children's National Hospital, George Washington University School of Medicine and Health Sciences, Washington, DC, 20012, USA
- Del Monte Institute for Neuroscience, Department of Neuroscience, University of Rochester School of Medicine and Dentistry, Rochester, NY, 14642, USA
| | - Steven Stufflebeam
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, 02129, USA
| | - Yi-Fen Yen
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, 02129, USA
| | - Alexander Lin
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, 02129, USA
| | - Bruce G Jenkins
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, 02129, USA
| | - Lilianne R Mujica-Parodi
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, 02129, USA
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY, 11794, USA
- Laufer Center for Physical and Quantitative Biology, Stony Brook University, Stony Brook, NY, 11794, USA
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Eva-Maria Ratai
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, 02129, USA.
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3
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Štětkářová I, Keller J. Modulation of Motor Cortex Activity After Intrathecal Baclofen Delivery in Chronic Thoracic Spinal Cord Injury. Front Neurol 2022; 13:778697. [PMID: 35645987 PMCID: PMC9136289 DOI: 10.3389/fneur.2022.778697] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Accepted: 04/04/2022] [Indexed: 11/13/2022] Open
Abstract
ObjectivesIntrathecal baclofen (ITB) is commonly used for reduction of spasticity in chronic spinal cord injury (SCI). Its clinical effect is well-known; however, exact mechanisms of long-term effect of continuous ITB administration (cITBa) on modulation of cortical processes have not been elucidated. The aim of this study was to evaluate changes in motor cortex activation for healthy upper limbs in comparison to impaired lower limbs by functional magnetic resonance imaging (fMRI).MethodsTen subjects (eight males, 20–69 years) with thoracic SCI presenting no voluntary movements of lower limbs (except one) were enrolled in the fMRI study. fMRI at 1.5T with a finger tapping paradigm and mental movement simulating foot flexion on the dominant side were performed before, 3 months, and 1 year after start of cITBa. fMRI data processing was carried out using FMRI Expert Analysis Tool (FEAT), part of FSL. A second-level analysis was carried out using FLAME stages 1 and 2. The level of spasticity was assessed with the Modified Ashworth scale (MAS).ResultsContinuous ITB significantly decreased limb spasticity in all the subjects (group MAS spasticity dropped from 3 to 0.3). The second-level analysis (Z > 1.6, cluster significance threshold p =0.05) revealed increased activation of the primary sensorimotor cortex of the foot between baseline and 3 months, and 3 months and 1 year.ConclusionIncreased sensorimotor cortex activation with spasticity reduction after cITBa may reflect distant functional reorganization because of long-term mediated neuroplastic changes in the sensorimotor cortex. Better understanding of modulation of brain function in SCI after cITBa may influence the field of neurorehabilitation.
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Affiliation(s)
- Ivana Štětkářová
- Department of Neurology, Third Faculty of Medicine, Královské Vinohrady University Hospital, Prague, Czechia
- *Correspondence: Ivana Štětkářová
| | - Jiří Keller
- Department of Neurology, Third Faculty of Medicine, Královské Vinohrady University Hospital, Prague, Czechia
- Department of Radiology, Na Homolce Hospital, Prague, Czechia
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4
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Furlong TM, Duncan JR, Corbit LH, Rae CD, Rowlands BD, Maher AD, Nasrallah FA, Milligan CJ, Petrou S, Lawrence AJ, Balleine BW. Toluene inhalation in adolescent rats reduces flexible behaviour in adulthood and alters glutamatergic and GABAergic signalling. J Neurochem 2016; 139:806-822. [PMID: 27696399 DOI: 10.1111/jnc.13858] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2016] [Revised: 09/15/2016] [Accepted: 09/18/2016] [Indexed: 12/24/2022]
Abstract
Toluene is a commonly abused inhalant that is easily accessible to adolescents. Despite the increasing incidence of use, our understanding of its long-term impact remains limited. Here, we used a range of techniques to examine the acute and chronic effects of toluene exposure on glutameteric and GABAergic function, and on indices of psychological function in adult rats after adolescent exposure. Metabolomics conducted on cortical tissue established that acute exposure to toluene produces alterations in cellular metabolism indicative of a glutamatergic and GABAergic profile. Similarly, in vitro electrophysiology in Xenopus oocytes found that acute toluene exposure reduced NMDA receptor signalling. Finally, in an adolescent rodent model of chronic intermittent exposure to toluene (10 000 ppm), we found that, while toluene exposure did not affect initial learning, it induced a deficit in updating that learning when response-outcome relationships were reversed or degraded in an instrumental conditioning paradigm. There were also group differences when more effort was required to obtain the reward; toluene-exposed animals were less sensitive to progressive ratio schedules and to delayed discounting. These behavioural deficits were accompanied by changes in subunit expression of both NMDA and GABA receptors in adulthood, up to 10 weeks after the final exposure to toluene in the hippocampus, prefrontal cortex and ventromedial striatum; regions with recognized roles in behavioural flexibility and decision-making. Collectively, our data suggest that exposure to toluene is sufficient to induce adaptive changes in glutamatergic and GABAergic systems and in adaptive behaviour that may underlie the deficits observed following adolescent inhalant abuse, including susceptibility to further drug-use.
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Affiliation(s)
- Teri M Furlong
- Brain & Mind Centre, University of Sydney, Sydney, New South Wales, Australia.,School of Psychology, University of Sydney, Sydney, New South Wales, Australia
| | - Jhodie R Duncan
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia.,Department of Anatomy and Neuroscience, University of Melbourne, Melbourne, Victoria, Australia
| | - Laura H Corbit
- School of Psychology, University of Sydney, Sydney, New South Wales, Australia
| | - Caroline D Rae
- Neuroscience Research Australia, Randwick, New South Wales, Australia.,School of Medical Sciences, University of NSW, Kensington, New South Wales, Australia
| | - Benjamin D Rowlands
- Neuroscience Research Australia, Randwick, New South Wales, Australia.,School of Medical Sciences, University of NSW, Kensington, New South Wales, Australia
| | - Anthony D Maher
- Neuroscience Research Australia, Randwick, New South Wales, Australia
| | | | - Carol J Milligan
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - Steven Petrou
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - Andrew J Lawrence
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - Bernard W Balleine
- Brain & Mind Centre, University of Sydney, Sydney, New South Wales, Australia.,School of Psychology, University of NSW, Kensington, New South Wales, Australia
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Rae C, Nasrallah FA, Balcar VJ, Rowlands BD, Johnston GAR, Hanrahan JR. Metabolomic Approaches to Defining the Role(s) of GABAρ Receptors in the Brain. J Neuroimmune Pharmacol 2015; 10:445-56. [PMID: 25577264 DOI: 10.1007/s11481-014-9579-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2014] [Accepted: 12/26/2014] [Indexed: 10/24/2022]
Abstract
The inhibitory neurotransmitter γ-aminobutyric acid (GABA) acts through various types of receptors in the central nervous system. GABAρ receptors, defined by their characteristic pharmacology and presence of ρ subunits in the channel structure, are poorly understood and their role in the cortex is ill-defined. Here, we used a targeted pharmacological, NMR-based functional metabolomic approach in Guinea pig brain cortical tissue slices to identify a distinct role for these receptors. We compared metabolic fingerprints generated by a range of ligands active at GABAρ and included these in a principal components analysis with a library of other metabolic fingerprints obtained using ligands active at GABAA and GABAB, with inhibitors of GABA uptake and with compounds acting to inhibit enzymes active in the GABAergic system. This enabled us to generate a metabolic "footprint" of the GABAergic system which revealed classes of metabolic activity associated with GABAρ which are distinct from other GABA receptors. Antagonised GABAρ produce large metabolic effects at extrasynaptic sites suggesting they may be involved in tonic inhibition.
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Affiliation(s)
- Caroline Rae
- Neuroscience Research Australia, Barker St, Randwick, NSW, 2031, Australia,
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6
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Rae C, Balcar VJ. A Chip Off the Old Block: The Brain Slice as a Model for Metabolic Studies of Brain Compartmentation and Neuropharmacology. BRAIN ENERGY METABOLISM 2014. [DOI: 10.1007/978-1-4939-1059-5_10] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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7
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Rae CD, Davidson JE, Maher AD, Rowlands BD, Kashem MA, Nasrallah FA, Rallapalli SK, Cook JM, Balcar VJ. Ethanol, not detectably metabolized in brain, significantly reduces brain metabolism, probably via action at specific GABA(A) receptors and has measureable metabolic effects at very low concentrations. J Neurochem 2013; 129:304-14. [PMID: 24313287 DOI: 10.1111/jnc.12634] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2013] [Revised: 11/12/2013] [Accepted: 12/04/2013] [Indexed: 11/28/2022]
Abstract
Ethanol is a known neuromodulatory agent with reported actions at a range of neurotransmitter receptors. Here, we measured the effect of alcohol on metabolism of [3-¹³C]pyruvate in the adult Guinea pig brain cortical tissue slice and compared the outcomes to those from a library of ligands active in the GABAergic system as well as studying the metabolic fate of [1,2-¹³C]ethanol. Analyses of metabolic profile clusters suggest that the significant reductions in metabolism induced by ethanol (10, 30 and 60 mM) are via action at neurotransmitter receptors, particularly α4β3δ receptors, whereas very low concentrations of ethanol may produce metabolic responses owing to release of GABA via GABA transporter 1 (GAT1) and the subsequent interaction of this GABA with local α5- or α1-containing GABA(A)R. There was no measureable metabolism of [1,2-¹³C]ethanol with no significant incorporation of ¹³C from [1,2-¹³C]ethanol into any measured metabolite above natural abundance, although there were measurable effects on total metabolite sizes similar to those seen with unlabelled ethanol.
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Affiliation(s)
- Caroline D Rae
- Neuroscience Research Australia, and Brain Sciences UNSW, Randwick, NSW, Australia
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8
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Rae CD. A Guide to the Metabolic Pathways and Function of Metabolites Observed in Human Brain 1H Magnetic Resonance Spectra. Neurochem Res 2013; 39:1-36. [PMID: 24258018 DOI: 10.1007/s11064-013-1199-5] [Citation(s) in RCA: 327] [Impact Index Per Article: 29.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2013] [Revised: 11/08/2013] [Accepted: 11/11/2013] [Indexed: 12/20/2022]
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9
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Metabolism, Compartmentation, Transport and Production of Acetate in the Cortical Brain Tissue Slice. Neurochem Res 2012; 37:2541-53. [DOI: 10.1007/s11064-012-0847-5] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2012] [Revised: 07/12/2012] [Accepted: 07/13/2012] [Indexed: 10/28/2022]
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10
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Nasrallah FA, Balcar VJ, Rae CD. Activity-dependent γ-aminobutyric acid release controls brain cortical tissue slice metabolism. J Neurosci Res 2011; 89:1935-45. [DOI: 10.1002/jnr.22649] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2010] [Revised: 02/15/2011] [Accepted: 03/01/2011] [Indexed: 12/16/2022]
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Nasrallah FA, Maher AD, Hanrahan JR, Balcar VJ, Rae CD. γ-Hydroxybutyrate and the GABAergic footprint: a metabolomic approach to unpicking the actions of GHB. J Neurochem 2010; 115:58-67. [PMID: 20681954 DOI: 10.1111/j.1471-4159.2010.06901.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Gamma-hydroxybutyrate is found both naturally in the brain and self-administered as a drug of abuse. It has been reported to act at endogenous γ-hydroxybutyrate (GHB) receptors and GABA(B) receptors [GABA(B)R], and may also be metabolized to GABA. Here, the metabolic fingerprints of a range of concentrations of GHB were measured in brain cortical tissue slices and compared with those of ligands active at GHB and GABA-R using principal components analysis (PCA) to identify sites of GHB activity. Low concentrations of GHB (1.0 μM) produced fingerprints similar to those of ligands active at GHB receptors and α4-containing GABA(A)R. A total of 10 μM GHB clustered proximate to mainstream GABAergic synapse ligands, such as 1.0 μM baclofen, a GABA(B)R agonist. Higher concentrations of GHB (30 μM) clustered with GABA(C)R agonists and the metabolic responses induced by blockade of the GABA transporter-1 (GAT1). The metabolic responses induced by 60 and 100 μM GHB were mimicked by simultaneous blockade of GAT1 and GAT3, addition of low concentrations of GABA(C)R antagonists, or increasing cytoplasmic GABA concentrations by incubation with the GABA transaminase inhibitor vigabatrin. These data suggest that at concentrations > 30 μM, GHB may be active via metabolism to GABA, which is then acting upon an unidentified GABAergic master switch receptor (possibly a high-affinity extrasynaptic receptor), or GHB may itself be acting directly on an extrasynaptic GABA-R, capable of turning off large numbers of cells. These results offer an explanation for the steep dose-response curve of GHB seen in vivo, and suggest potential target receptors for further investigation.
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Sonnewald U, Rae C. Pyruvate carboxylation in different model systems studied by (13)C MRS. Neurochem Res 2010; 35:1916-21. [PMID: 20842423 PMCID: PMC3002159 DOI: 10.1007/s11064-010-0257-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/26/2010] [Indexed: 11/17/2022]
Abstract
Pyruvate carboxylation is of great importance in the brain since it is responsible for adding net carbons to the tricarboxylic acid cycle following removal of carbon backbone for synthesis of the two most abundant neurotransmitters, glutamate and GABA. Despite having such a pivotal role, there is still much uncertainty in the exact metabolic details about where and how this carbon is returned. Pyruvate carboxylation has been studied in various model systems of the brain and 13C magnetic resonance spectroscopy is an excellent tool for doing this. This review will focus on results dealing with the extent and cellular location of pyruvate carboxylation and its role in pathophysiology and concludes that pyruvate carboxylation is an extraordinarily important predominantly astrocytic pathway which plays a pivotal part in a number of diseases.
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Affiliation(s)
- Ursula Sonnewald
- Department of Neuroscience, Norwegian University of Science and Technology, 7489 Trondheim, Norway.
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13
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Rae C, Nasrallah FA, Griffin JL, Balcar VJ. Now I know my ABC. A systems neurochemistry and functional metabolomic approach to understanding the GABAergic system. J Neurochem 2009; 109 Suppl 1:109-16. [DOI: 10.1111/j.1471-4159.2009.05803.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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14
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Rae C, Nasrallah FA, Bröer S. Metabolic effects of blocking lactate transport in brain cortical tissue slices using an inhibitor specific to MCT1 and MCT2. Neurochem Res 2009; 34:1783-91. [PMID: 19404741 DOI: 10.1007/s11064-009-9973-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2009] [Accepted: 04/07/2009] [Indexed: 11/25/2022]
Abstract
A novel inhibitor of lactate transport, AR-C122982, was used to study the effect of inhibiting the monocarboxylate transporters MCT1 and MCT2 on cortical brain slice metabolism. We studied metabolism of L-[3-13C]lactate, and D-[1-13C]glucose under a range of conditions. Experiments using L-[3-13C]lactate showed that the inhibitor AR-C122982 altered exchange of lactate. Under depolarizing conditions, net flux of label from D-[1-13C]glucose was barely altered by 10 or 100 nM AR-C122982. In the presence of AMPA or glutamate there were increases in net flux of label and metabolic pool sizes. These data suggest lactate may supply compartments in the brain not usually directly accessed by glucose. In general, it would appear that movement of lactate between cell types is not essential for metabolic activity, with the heavy metabolic workloads imposed being unaffected by inhibition of MCT1 and MCT2. Further experiments investigating the mechanism of operation of AR-C122982 are necessary to corroborate this finding.
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Affiliation(s)
- Caroline Rae
- Prince of Wales Medical Research Institute, Barker St., Randwick, NSW 2031, Australia.
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15
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Nasrallah FA, Griffin JL, Balcar VJ, Rae C. Understanding your inhibitions: effects of GABA and GABAAreceptor modulation on brain cortical metabolism. J Neurochem 2009; 108:57-71. [DOI: 10.1111/j.1471-4159.2008.05742.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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16
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Riera JJ, Schousboe A, Waagepetersen HS, Howarth C, Hyder F. The micro-architecture of the cerebral cortex: functional neuroimaging models and metabolism. Neuroimage 2008; 40:1436-59. [PMID: 18343162 PMCID: PMC4348032 DOI: 10.1016/j.neuroimage.2007.12.051] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2007] [Revised: 12/19/2007] [Accepted: 12/20/2007] [Indexed: 01/22/2023] Open
Abstract
In order to interpret/integrate data obtained with different functional neuroimaging modalities (e.g. fMRI, EEG/MEG, PET/SPECT, fNIRS), forward-generative models of a diversity of brain mechanisms at the mesoscopic level are considered necessary. For the cerebral cortex, the brain structure with possibly the most relevance for functional neuroimaging, a variety of such biophysical models has been proposed over the last decade. The development of technological tools to investigate in vitro the physiological, anatomical and biochemical principles at the microscopic scale in comparative studies formed the basis for such theoretical progresses. However, with the most recent introduction of systems to record electrical (e.g. miniaturized probes chronically/acutely implantable in the brain), optical (e.g. two-photon laser scanning microscopy) and atomic nuclear spectral (e.g. nuclear magnetic resonance spectroscopy) signals using living laboratory animals, the field is receiving even greater attention. Major advances have been achieved by combining such sophisticated recording systems with new experimental strategies (e.g. transgenic/knock-out animals, high resolution stereotaxic manipulation systems for probe-guidance and cellular-scale chemical-delivery). Theoreticians may now be encouraged to re-consider previously formulated mesoscopic level models in order to incorporate important findings recently made at the microscopic scale. In this series of reviews, we summarize the background at the microscopic scale, which we suggest will constitute the foundations for upcoming representations at the mesoscopic level. In this first part, we focus our attention on the nerve ending particles in order to summarize basic principles and mechanisms underlying cellular metabolism in the cerebral cortex. It will be followed by two parts highlighting major features in its organization/working-principles to regulate both cerebral blood circulation and neuronal activity, respectively. Contemporary theoretical models for functional neuroimaging will be revised in the fourth part, with particular emphasis in their applications, advantages/limitations and future prospects.
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Affiliation(s)
- Jorge J Riera
- Institute of Development, Aging and Cancer, Tohoku University, Sendai, Japan.
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17
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Dambrova M, Zvejniece L, Liepinsh E, Cirule H, Zharkova O, Veinberg G, Kalvinsh I. Comparative pharmacological activity of optical isomers of phenibut. Eur J Pharmacol 2008; 583:128-34. [DOI: 10.1016/j.ejphar.2008.01.015] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2007] [Revised: 12/14/2007] [Accepted: 01/14/2008] [Indexed: 11/28/2022]
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18
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Neggers SFW, Huijbers W, Vrijlandt CM, Vlaskamp BNS, Schutter DJLG, Kenemans JL. TMS Pulses on the Frontal Eye Fields Break Coupling Between Visuospatial Attention and Eye Movements. J Neurophysiol 2007; 98:2765-78. [PMID: 17699696 DOI: 10.1152/jn.00357.2007] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
While preparing a saccadic eye movement, visual processing of the saccade goal is prioritized. Here, we provide evidence that the frontal eye fields (FEFs) are responsible for this coupling between eye movements and shifts of visuospatial attention. Functional magnetic resonance imaging (fMRI)–guided transcranial magnetic stimulation (TMS) was applied to the FEFs 30 ms before a discrimination target was presented at or next to the target of a saccade in preparation. Results showed that the well-known enhancement of discrimination performance on locations to which eye movements are being prepared was diminished by TMS contralateral to eye movement direction. Based on the present and other reports, we propose that saccade preparatory processes in the FEF affect selective visual processing within the visual cortex through feedback projections, in that way coupling saccade preparation and visuospatial attention.
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Affiliation(s)
- S F W Neggers
- Experimental Psychology, Helmholtz Institute, Utrecht University, The Netherlands.
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19
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Nasrallah FA, Garner B, Ball GE, Rae C. Modulation of brain metabolism by very low concentrations of the commonly used drug delivery vehicle dimethyl sulfoxide (DMSO). J Neurosci Res 2007; 86:208-14. [PMID: 17853437 DOI: 10.1002/jnr.21477] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Dimethyl sulfoxide (DMSO) has long been used in studies as a vehicle to enhance the solubility and transport of ligands in biological systems. The effects of this drug on the outcomes of such studies are still unclear, with concentrations of DMSO reported as "safe" varying considerably. In the present work, we investigated the effects of very low concentrations of DMSO on the brain metabolism of [3-(13)C]pyruvate and D-[1-(13)C]glucose using (1)H/(13)C NMR spectroscopy and a guinea pig cortical brain slice model. Our results show that DMSO is accumulated by brain slices. DMSO at all concentrations [0.000025%-0.25% (v/v)] increased the metabolic rate when [3-(13)C]pyruvate was used as a substrate and also in the presence of D-[1-(13)C]glucose (0.00025%-0.1% DMSO). These results are consistent with DMSO stimulating respiration, which it may do through altering the kinetics of ATP-requiring reactions. Our results also emphasize that there is no practical concentration of DMSO that can be used in metabolic experiments without effect. Therefore, care should be taken when evaluating the actions of drugs administered in combination with DMSO.
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