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O’Kelly D, Guo Y, Mason RP. Evaluating online filtering algorithms to enhance dynamic multispectral optoacoustic tomography. Photoacoustics 2020; 19:100184. [PMID: 32509522 PMCID: PMC7264082 DOI: 10.1016/j.pacs.2020.100184] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Revised: 04/16/2020] [Accepted: 04/17/2020] [Indexed: 06/11/2023]
Abstract
Multispectral optoacoustic tomography (MSOT) is an emerging imaging modality, which is able to capture data at high spatiotemporal resolution using rapid tuning of the excitation laser wavelength. However, owing to the necessity of imaging one wavelength at a time to the exclusion of others, forming a complete multispectral image requires multiple excitations over time, which may introduce aliasing due to underlying spectral dynamics or noise in the data. In order to mitigate this limitation, we have applied kinematic α and α β filters to multispectral time series, providing an estimate of the underlying multispectral image at every point in time throughout data acquisition. We demonstrate the efficacy of these methods in suppressing the inter-frame noise present in dynamic multispectral image time courses using a multispectral Shepp-Logan phantom and mice bearing distinct renal cell carcinoma tumors. The gains in signal to noise ratio provided by these filters enable higher-fidelity downstream analysis such as spectral unmixing and improved hypothesis testing in quantifying the onset of signal changes during an oxygen gas challenge.
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Affiliation(s)
- Devin O’Kelly
- Department of Radiology, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX, 75390-9058, USA
| | - Yihang Guo
- Department of Radiology, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX, 75390-9058, USA
- Department of Gastrointestinal Surgery, The Third XiangYa Hospital of Central South University, Changsha, Hunan, 410013, China
| | - Ralph P. Mason
- Department of Radiology, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX, 75390-9058, USA
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Crofts A, Trotman-Lucas M, Janus J, Kelly M, Gibson CL. A longitudinal, multi-parametric functional MRI study to determine age-related changes in the rodent brain. Neuroimage 2020; 218:116976. [PMID: 32464290 PMCID: PMC7422839 DOI: 10.1016/j.neuroimage.2020.116976] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2020] [Revised: 04/24/2020] [Accepted: 05/19/2020] [Indexed: 02/07/2023] Open
Abstract
As the population ages, the incidence of age-related neurological diseases and cognitive decline increases. To further understand disease-related changes in brain function it is advantageous to examine brain activity changes in healthy aging rodent models to permit mechanistic investigation. Here, we examine the suitability, in rodents, of using a novel, minimally invasive anaesthesia protocol in combination with a functional MRI protocol to assess alterations in neuronal activity due to physiological aging. 11 Wistar Han female rats were studied at 7, 9, 12, 15 and 18 months of age. Under an intravenous infusion of propofol, animals underwent functional magnetic resonance imaging (fMRI) and functional magnetic resonance spectroscopy (fMRS) with forepaw stimulation to quantify neurotransmitter activity, and resting cerebral blood flow (CBF) quantification using arterial spin labelling (ASL) to study changes in neurovascular coupling over time. Animals showed a significant decrease in size of the active region with age (P < 0.05). fMRS results showed a significant decrease in glutamate change with stimulation (ΔGlu) with age (P < 0.05), and ΔGlu became negative from 12 months onwards. Global CBF remained constant for the duration of the study. This study shows age related changes in the blood oxygen level dependent (BOLD) response in rodents that correlate with those seen in humans. The results also suggest that a reduction in synaptic glutamate turnover with age may underlie the reduction in the BOLD response, while CBF is preserved. Describe a novel anaesthetic protocol to examine age-related alterations in neuronal activity in rodents. Size of the BOLD signal in the somatosensory cortex decreased with age. Reduction in glutamate turnover with age. No change in resting CBF with age.
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Affiliation(s)
- Andrew Crofts
- Department of Neuroscience, Psychology & Behaviour, University of Leicester, Leicester, UK; Preclinical Imaging Facility, Core Biotechnology Services, University of Leicester, Leicester, UK
| | - Melissa Trotman-Lucas
- Department of Neuroscience, Psychology & Behaviour, University of Leicester, Leicester, UK; School of Psychology, University of Nottingham, Nottingham, UK
| | - Justyna Janus
- Preclinical Imaging Facility, Core Biotechnology Services, University of Leicester, Leicester, UK
| | - Michael Kelly
- Preclinical Imaging Facility, Core Biotechnology Services, University of Leicester, Leicester, UK
| | - Claire L Gibson
- Department of Neuroscience, Psychology & Behaviour, University of Leicester, Leicester, UK; School of Psychology, University of Nottingham, Nottingham, UK.
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Crofts A, Kelly ME, Gibson CL. Imaging Functional Recovery Following Ischemic Stroke: Clinical and Preclinical fMRI Studies. J Neuroimaging 2019; 30:5-14. [PMID: 31608550 PMCID: PMC7003729 DOI: 10.1111/jon.12668] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2019] [Revised: 09/12/2019] [Accepted: 09/25/2019] [Indexed: 12/18/2022] Open
Abstract
Disability and effectiveness of physical therapy are highly variable following ischemic stroke due to different brain regions being affected. Functional magnetic resonance imaging (fMRI) studies of patients in the months and years following stroke have given some insight into how the brain recovers lost functions. Initially, new pathways are recruited to compensate for the lost region, showing as a brighter blood oxygen‐level‐dependent (BOLD) signal over a larger area during a task than in healthy controls. Subsequently, activity is reduced to baseline levels as pathways become more efficient, mimicking the process of learning typically seen during development. Preclinical models of ischemic stroke aim to enhance understanding of the biology underlying recovery following stroke. However, the pattern of recruitment and focusing seen in humans has not been observed in preclinical fMRI studies that are highly variable methodologically. Resting‐state fMRI studies show more consistency; however, there are still confounding factors to address. Anesthesia and method of stroke induction are the two main sources of variability in preclinical studies; improvements here can reduce variability and increase the intensity and reproducibility of the BOLD response detected by fMRI. Differences in task or stimulus and differences in analysis method also present a source of variability. This review compares clinical and preclinical fMRI studies of recovery following stroke and focuses on how refinement of preclinical models and MRI methods may obtain more representative fMRI data in relation to human studies.
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Affiliation(s)
- Andrew Crofts
- Department of Neuroscience, Psychology and Behaviour, University of Leicester, Leicester, UK
| | - Michael E Kelly
- Preclinical Imaging Facility, Core Biotechnology Services, University of Leicester, Leicester, UK
| | - Claire L Gibson
- School of Psychology, University of Nottingham, Nottingham, UK
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Gormley S, Rouine J, McIntosh A, Kerskens C, Harkin A. Glial fibrillary acidic protein (GFAP) immunoreactivity correlates with cortical perfusion parameters determined by bolus tracking arterial spin labelling (bt-ASL) magnetic resonance (MR) imaging in the Wistar Kyoto rat. Physiol Behav 2016; 160:66-79. [PMID: 27068181 DOI: 10.1016/j.physbeh.2016.04.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [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: 01/27/2016] [Revised: 03/21/2016] [Accepted: 04/06/2016] [Indexed: 12/14/2022]
Abstract
Alterations in astrocyte number and function have been implicated in the pathophysiology of a number of psychiatric disorders. The development of magnetic resonance imaging (MRI) as a tool in the animal laboratory has enabled an investigation of the relationship between pathological and neuroimaging markers in animal models. However the physiological processes which underlie these markers and their role in mediating behavioural deficits is still poorly understood. Rodent models have provided us with important insights into physiological and cellular mechanisms which may mediate anxiety and depression-related behaviours. The Wistar-Kyoto (WKY) rat is a strain which endogenously expresses highly anxious and depressive-like behaviours and has previously been reported to exhibit alterations in immunoreactivity for the astrocytic marker glial fibrillary acidic protein (GFAP) in brain sub-regions relative to more stress resilient out-bred strains. Here we report that the depressive and anxiety-like behaviours exhibited by the WKY rat strain are associated with alterations in brain morphology including a decrease in hippocampal volume, coupled with reduced resting state frontal cortical perfusion as assessed by MR bolus tracking arterial spin labelling (bt-ASL) relative to the out-bred Wistar strain. Pre-limbic cortical GFAP immunoreactivity and astrocyte cell number were positively correlated with cortical blood perfusion in the WKY strain. These experiments provide a link between pathological and neuroimaging markers of aberrant astrocytic function and add validity to the WKY rat as a model for co-morbid anxiety and depression.
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Affiliation(s)
- Shane Gormley
- Neuropsychopharmacology Research Group, School of Pharmacy & Pharmaceutical Sciences, Dublin, Ireland.
| | - Jennifer Rouine
- Neuropsychopharmacology Research Group, School of Pharmacy & Pharmaceutical Sciences, Dublin, Ireland; Trinity College Institute of Neuroscience, Dublin, Ireland
| | | | | | - Andrew Harkin
- Neuropsychopharmacology Research Group, School of Pharmacy & Pharmaceutical Sciences, Dublin, Ireland; Trinity College Institute of Neuroscience, Dublin, Ireland.
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He T, Cao L, Balas VE, McCauley P, Shi F. Curvature manipulation of the spectrum of Valence-Arousal-related fMRI dataset using Gaussian-shaped Fast Fourier Transform and its application to fuzzy KANSEI adjectives modeling. Neurocomputing 2016. [DOI: 10.1016/j.neucom.2015.10.025] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
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Rouine J, Kelly ME, Jennings-Murphy C, Duffy P, Gorman I, Gormley S, Kerskens CM, Harkin A. Investigation of the mechanisms mediating MDMA "Ecstasy"-induced increases in cerebro-cortical perfusion determined by btASL MRI. Psychopharmacology (Berl) 2015; 232:1501-13. [PMID: 25366875 DOI: 10.1007/s00213-014-3790-0] [Citation(s) in RCA: 3] [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] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/16/2014] [Accepted: 10/19/2014] [Indexed: 01/16/2023]
Abstract
RATIONALE Acute administration of the recreational drug of abuse 3,4-methylenedioxymethamphetamine (MDMA; Ecstasy) has previously been shown to increase cerebro-cortical perfusion as determined by bolus-tracking arterial spin labelling (btASL) MRI. OBJECTIVES The purpose of the current study was to assess the mechanisms mediating these changes following systemic administration of MDMA to rats. METHODS Pharmacological manipulation of serotonergic, dopaminergic and nitrergic transmission was carried out to determine the mechanism of action of MDMA-induced increases in cortical perfusion using btASL MRI. RESULTS Fenfluramine (10 mg/kg), like MDMA (20 mg/kg), increased cortical perfusion. Increased cortical perfusion was not obtained with the 5-HT2 receptor agonist 2,5-dimethoxy-4-iodophenyl-aminopropane hydrochloride (DOI) (1 mg/kg). Depletion of central 5-HT following systemic administration of the tryptophan hydroxylase inhibitor para-chlorophenylalanine (pCPA) produced effects similar to those observed with MDMA. Pre-treatment with the 5-HT receptor antagonist metergoline (4 mg/kg) or with the 5-HT reuptake inhibitor citalopram (30 mg/kg), however, failed to produce any effect alone or influence the response to MDMA. Pre-treatment with the dopamine D1 receptor antagonist SCH 23390 (1 mg/kg) failed to influence the changes in cortical perfusion obtained with MDMA. Treatment with the neuronal nitric oxide (NO) synthase inhibitor 7-nitroindazole (7-NI) (25 mg/kg) provoked no change in cerebral perfusion alone yet attenuated the MDMA-related increase in cortical perfusion. CONCLUSIONS Cortical 5-HT depletion is associated with increases in perfusion although this mechanism alone does not account for MDMA-related changes. A role for NO, a key regulator of cerebrovascular perfusion, is implicated in MDMA-induced increases in cortical perfusion.
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Affiliation(s)
- J Rouine
- Trinity College Institute of Neuroscience, Trinity College, Dublin, 2, Ireland
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Rouine J, Gobbo OL, Campbell M, Gigliucci V, Ogden I, McHugh Smith K, Duffy P, Behan B, Byrne D, Kelly ME, Blau CW, Kerskens CM, Harkin A. MDMA 'ecstasy' increases cerebral cortical perfusion determined by bolus-tracking arterial spin labelling (btASL) MRI. Br J Pharmacol 2015; 169:974-87. [PMID: 23517012 DOI: 10.1111/bph.12178] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Revised: 12/10/2012] [Accepted: 02/18/2013] [Indexed: 11/26/2022] Open
Abstract
BACKGROUND AND PURPOSE The purpose of this study was to assess cerebral perfusion changes following systemic administration of the recreational drug 3,4-methylendioxymethamphetamine (MDMA 'ecstasy') to rats. EXPERIMENTAL APPROACH Cerebral perfusion was quantified using bolus-tracking arterial spin labelling (btASL) MRI. Rats received MDMA (20 mg·kg(-1); i.p.) and were assessed 1, 3 or 24 h later. Rats received MDMA (5 or 20 mg·kg(-1); i.p.) and were assessed 3 h later. In addition, rats received MDMA (5 or 10 mg·kg(-1); i.p.) or saline four times daily over 2 consecutive days and were assessed 8 weeks later. Perfusion-weighted images were generated in a 7 tesla (7T) MRI scanner and experimental data was fitted to a quantitative model of cerebral perfusion to generate mean transit time (MTT), capillary transit time (CTT) and signal amplitude. KEY RESULTS MDMA reduces MTT and CTT and increases amplitude in somatosensory and motor cortex 1 and 3 h following administration, indicative of an increase in perfusion. Prior exposure to MDMA provoked a long-term reduction in cortical 5-HT concentration, but did not produce a sustained effect on cerebral cortical perfusion. The response to acute MDMA challenge (20 mg·kg(-1); i.p.) was attenuated in these animals indicating adaptation in response to prior MDMA exposure. CONCLUSIONS AND IMPLICATIONS MDMA provokes changes in cortical perfusion, which are quantifiable by btASL MRI, a neuroimaging tool with translational potential. Future studies are directed towards elucidation of the mechanisms involved and correlating changes in cerebrovascular function with potential behavioural deficits associated with drug use.
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Affiliation(s)
- J Rouine
- Trinity College Institute of Neuroscience, Trinity College Dublin, Dublin, Ireland
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Gigliucci V, Gormley S, Gibney S, Rouine J, Kerskens C, Connor TJ, Harkin A. Characterisation of the antidepressant properties of nitric oxide synthase inhibitors in the olfactory bulbectomised rat model of depression. Eur Neuropsychopharmacol 2014; 24:1349-61. [PMID: 24931298 DOI: 10.1016/j.euroneuro.2014.05.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/12/2013] [Revised: 04/11/2014] [Accepted: 05/09/2014] [Indexed: 02/05/2023]
Abstract
Nitric oxide synthase (NOS) inhibitors possess antidepressant-like properties in preclinical tests and in the current investigation the brain penetrant NOS inhibitor N(ω)-nitro-L-arginine (l-NA) and the preferential inhibitor of neuronal NOS (nNOS) 1-(2-trifluoromethylphenyl) imidazole (TRIM) were assessed in the olfactory bulbectomised (OB) rat, a well-established animal model of depression. Magnetic resonance imaging (MRI) was employed to assess regional brain volumes, blood perfusion and T1 and T2 relaxometry times both with and without drug treatment. l-NA (10 mg/kg, once daily p.o. for 10 days) attenuated OB-related hyperactivity in the "open field" test in a comparable fashion to the tricyclic antidepressant imipramine (20 mg/kg, once daily p.o. for 14 days) indicative of an antidepressant-like response in the model. Treatment with TRIM (50 mg/kg, once daily s.c.) attenuated OB-related hyperactivity following 7 days of treatment when compared to vehicle treated controls. OB is associated with enlarged ventricular volume, increased periventicular perfusion and a decrease in T2 relaxation times in cortical and hippocampal regions, with enhanced perfusion and reduced T2 times attenuated by L-NA treatment. L-NA treatment was also associated with an increase in T1 relaxation times in limbic and cortical regions and found to reduce resting state hippocampal blood perfusion in OB animals. Behavioural observations are consistent with an antidepressant action of NOS inhibitors where associated changes in perfusion and T2 relaxation times may be related to the antidepressant action of L-NA in the model.
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Denieffe S, Kelly RJ, McDonald C, Lyons A, Lynch MA. Classical activation of microglia in CD200-deficient mice is a consequence of blood brain barrier permeability and infiltration of peripheral cells. Brain Behav Immun 2013; 34:86-97. [PMID: 23916893 DOI: 10.1016/j.bbi.2013.07.174] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/29/2013] [Revised: 07/22/2013] [Accepted: 07/29/2013] [Indexed: 01/08/2023] Open
Abstract
The interaction between CD200, expressed on several cell types, and its receptor CD200R, expressed on cells of the myeloid lineage, has been shown to be an important factor in modulating inflammation in macrophage function in several conditions including colitis and arthritis. More recently its modulatory effect on microglial activation has been identified and CD200-deficiency has been associated with increased microglial activation accompanied by increased production of inflammatory cytokines. The response of glia prepared from CD200-deficient mice to stimuli like lipopolysaccharide (LPS) is markedly greater than the response of cells prepared from wildtype mice and, consistent with this, is the recent observation that expression of Toll-like receptor (TLR)4 and signalling through NFκB are increased in microglia prepared from CD200-deficient mice. Here we show that glia from CD200-deficient mice are also more responsive to interferon-γ (IFNγ) which triggers classical activation of microglia. We investigated the effects of CD200-deficiency in vivo and report that there is an increase in expression of several markers of microglial activation including tumor necrosis factor (TNF)-α, which is a hallmark of classically-activated microglia. These changes are accompanied by increased IFNγ, and the evidence suggests that this is produced by infiltrating cells including T cells and macrophages. We propose that these cells enter the brain as a consequence of increased blood brain barrier (BBB) permeability in CD200-deficient mice and that infiltration is assisted by increased expression of the chemokines, monocyte chemotactic protein-1 (MCP-1), IFNγ-induced protein-10 (IP-10) and RANTES. This may have implications in neurodegenerative diseases where BBB permeability is compromised.
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Nasrallah FA, Lee ELQ, Chuang KH. Optimization of flow-sensitive alternating inversion recovery (FAIR) for perfusion functional MRI of rodent brain. NMR Biomed 2012; 25:1209-1216. [PMID: 22451418 DOI: 10.1002/nbm.2790] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2011] [Revised: 12/02/2011] [Accepted: 01/17/2012] [Indexed: 05/31/2023]
Abstract
Arterial spin labeling (ASL) MRI provides a noninvasive method to image perfusion, and has been applied to map neural activation in the brain. Although pulsed labeling methods have been widely used in humans, continuous ASL with a dedicated neck labeling coil is still the preferred method in rodent brain functional MRI (fMRI) to maximize the sensitivity and allow multislice acquisition. However, the additional hardware is not readily available and hence its application is limited. In this study, flow-sensitive alternating inversion recovery (FAIR) pulsed ASL was optimized for fMRI of rat brain. A practical challenge of FAIR is the suboptimal global inversion by the transmit coil of limited dimensions, which results in low effective labeling. By using a large volume transmit coil and proper positioning to optimize the body coverage, the perfusion signal was increased by 38.3% compared with positioning the brain at the isocenter. An additional 53.3% gain in signal was achieved using optimized repetition and inversion times compared with a long TR. Under electrical stimulation to the forepaws, a perfusion activation signal change of 63.7 ± 6.3% can be reliably detected in the primary somatosensory cortices using single slice or multislice echo planar imaging at 9.4 T. This demonstrates the potential of using pulsed ASL for multislice perfusion fMRI in functional and pharmacological applications in rat brain.
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Affiliation(s)
- Fatima A Nasrallah
- Magnetic Resonance Imaging Group, Singapore Bioimaging Consortium, Agency for Science Technology and Research, Singapore
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Campbell M, Hanrahan F, Gobbo OL, Kelly ME, Kiang AS, Humphries MM, Nguyen AT, Ozaki E, Keaney J, Blau CW, Kerskens CM, Cahalan SD, Callanan JJ, Wallace E, Grant GA, Doherty CP, Humphries P. Targeted suppression of claudin-5 decreases cerebral oedema and improves cognitive outcome following traumatic brain injury. Nat Commun 2012; 3:849. [DOI: 10.1038/ncomms1852] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2011] [Accepted: 04/18/2012] [Indexed: 02/04/2023] Open
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Blau CW, Cowley TR, O'sullivan J, Grehan B, Browne TC, Kelly L, Birch A, Murphy N, Kelly AM, Kerskens CM, Lynch MA. The age-related deficit in LTP is associated with changes in perfusion and blood-brain barrier permeability. Neurobiol Aging 2012; 33:1005.e23-35. [DOI: 10.1016/j.neurobiolaging.2011.09.035] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2011] [Revised: 09/22/2011] [Accepted: 09/30/2011] [Indexed: 12/11/2022]
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Murphy N, Cowley TR, Blau CW, Dempsey CN, Noonan J, Gowran A, Tanveer R, Olango WM, Finn DP, Campbell VA, Lynch MA. The fatty acid amide hydrolase inhibitor URB597 exerts anti-inflammatory effects in hippocampus of aged rats and restores an age-related deficit in long-term potentiation. J Neuroinflammation 2012; 9:79. [PMID: 22537429 PMCID: PMC3409037 DOI: 10.1186/1742-2094-9-79] [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] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2012] [Accepted: 04/26/2012] [Indexed: 01/10/2023] Open
Abstract
BACKGROUND Several factors contribute to the deterioration in synaptic plasticity which accompanies age and one of these is neuroinflammation. This is characterized by increased microglial activation associated with increased production of proinflammatory cytokines like interleukin-1β (IL-1β). In aged rats these neuroinflammatory changes are associated with a decreased ability of animals to sustain long-term potentiation (LTP) in the dentate gyrus. Importantly, treatment of aged rats with agents which possess anti-inflammatory properties to decrease microglial activation, improves LTP. It is known that endocannabinoids, such as anandamide (AEA), have anti-inflammatory properties and therefore have the potential to decrease the age-related microglial activation. However, endocannabinoids are extremely labile and are hydrolyzed quickly after production. Here we investigated the possibility that inhibiting the degradation of endocannabinoids with the fatty acid amide hydrolase (FAAH) inhibitor, URB597, could ameliorate age-related increases in microglial activation and the associated decrease in LTP. METHODS Young and aged rats received subcutaneous injections of the FAAH inhibitor URB597 every second day and controls which received subcutaneous injections of 30% DMSO-saline every second day for 28 days. Long-term potentiation was recorded on day 28 and the animals were sacrificed. Brain tissue was analyzed for markers of microglial activation by PCR and for levels of endocannabinoids by liquid chromatography coupled to tandem mass spectrometry. RESULTS The data indicate that expression of markers of microglial activation, MHCII, and CD68 mRNA, were increased in the hippocampus of aged, compared with young, rats and that these changes were associated with increased expression of the proinflammatory cytokines interleukin (IL)-1β and tumor necrosis factor-α (TNFα) which were attenuated by treatment with URB597. Coupled with these changes, we observed an age-related decrease in LTP in the dentate gyrus which was partially restored in URB597-treated aged rats. The data suggest that enhancement of levels of endocannabinoids in the brain by URB597 has beneficial effects on synaptic function, perhaps by modulating microglial activation.
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Affiliation(s)
- Niamh Murphy
- Department of Physiology, Trinity College, Trinity College Institute for Neuroscience, Dublin 2, Ireland.
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Chinta LV, Lindvere L, Dorr A, Sahota B, Sled JG, Stefanovic B. Quantitative estimates of stimulation-induced perfusion response using two-photon fluorescence microscopy of cortical microvascular networks. Neuroimage 2012; 61:517-24. [PMID: 22521258 DOI: 10.1016/j.neuroimage.2012.04.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [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: 01/30/2012] [Revised: 03/30/2012] [Accepted: 04/03/2012] [Indexed: 01/29/2023] Open
Abstract
Functional hyperemia, or the increase in focal perfusion elicited by neuronal activation, is one of the primary functions of the neurovascular unit and a hallmark of healthy brain functioning. While much is known about the hemodynamics on the millimeter to tenths of millimeter-scale accessible by MRI, there is a paucity of quantitative data on the micrometer-scale changes in perfusion in response to functional stimulation. We present a novel methodology for quantification of perfusion and intravascular flow across the 3D microvascular network in the rat somatosensory cortex using two-photon fluorescence microscopy (2PFM). For approximately 96% of responding microvessels in the forelimb representation of the primary somatosensory cortex, brief (~2s) forepaw stimulation resulted in an increase of perfusion 20±4% (mean±sem). The perfusion levels associated with the remaining 4% of the responding microvessels decreased 10±9% upon stimulation. Vessels irrigating regions of lower vascular density were found to exhibit higher flow (p<0.02), supporting the notion that local vascular morphology and hemodynamics reflect the metabolic needs of the surrounding parenchyma. High dispersion (~77%) in perfusion levels suggests high spatial variation in tissue susceptibility to hypoxia. The current methodology enables quantification of absolute perfusion associated with individual vessels of the cortical microvascular bed and its changes in response to functional stimulation and thereby provides an important tool for studying the cellular mechanisms of functional hyperemia, the spatial specificity of perfusion response to functional stimulation, and, broadly, the micrometer-scale relationship between vascular morphology and function in health and disease.
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Affiliation(s)
- Lakshminarayan V Chinta
- Imaging Research, Sunnybrook Research Institute, 2075 Bayview Avenue, Toronto, ON, Canada M4N 3M5
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Oertel-knöchel V, Bittner RA, Knöchel C, Prvulovic D, Hampel H. Discovery and development of integrative biological markers for schizophrenia. Prog Neurobiol 2011; 95:686-702. [DOI: 10.1016/j.pneurobio.2011.05.006] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2011] [Revised: 05/25/2011] [Accepted: 05/27/2011] [Indexed: 12/30/2022]
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Pfefferbaum A, Chanraud S, Pitel AL, Müller-Oehring E, Shankaranarayanan A, Alsop DC, Rohlfing T, Sullivan EV. Cerebral blood flow in posterior cortical nodes of the default mode network decreases with task engagement but remains higher than in most brain regions. Cereb Cortex 2010; 21:233-44. [PMID: 20484322 DOI: 10.1093/cercor/bhq090] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Functional neuroimaging studies provide converging evidence for existence of intrinsic brain networks activated during resting states and deactivated with selective cognitive demands. Whether task-related deactivation of the default mode network signifies depressed activity relative to the remaining brain or simply lower activity relative to its resting state remains controversial. We employed 3D arterial spin labeling imaging to examine regional cerebral blood flow (CBF) during rest, a spatial working memory task, and a second rest. Change in regional CBF from rest to task showed significant normalized and absolute CBF reductions in posterior cingulate, posterior-inferior precuneus, and medial frontal lobes . A Statistical Parametric Mapping connectivity analysis, with an a priori seed in the posterior cingulate cortex, produced deactivation connectivity patterns consistent with the classic "default mode network" and activation connectivity anatomically consistent with engagement in visuospatial tasks. The large task-related CBF decrease in posterior-inferior precuneus relative to its anterior and middle portions adds evidence for the precuneus' heterogeneity. The posterior cingulate and posterior-inferior precuneus were also regions of the highest CBF at rest and during task performance. The difference in regional CBF between intrinsic (resting) and evoked (task) activity levels may represent functional readiness or reserve vulnerable to diminution by conditions affecting perfusion.
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Griffin KM, Blau CW, Kelly ME, O'Herlihy C, O'Connell PR, Jones JF, Kerskens CM. Propofol allows precise quantitative arterial spin labelling functional magnetic resonance imaging in the rat. Neuroimage 2010; 51:1395-404. [PMID: 20304075 DOI: 10.1016/j.neuroimage.2010.03.024] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2010] [Revised: 02/19/2010] [Accepted: 03/09/2010] [Indexed: 11/24/2022] Open
Abstract
Functional magnetic resonance imaging (fMRI) techniques highlight cerebral vascular responses which are coupled to changes in neural activation. However, two major difficulties arise when employing these techniques in animal studies. First is the disturbance of cerebral blood flow due to anaesthesia and second is the difficulty of precise reproducible quantitative measurements. These difficulties were surmounted in the current study by using propofol and quantitative arterial spin labelling (QASL) to measure relative cerebral blood volume of labelled water (rCBV(lw),) mean transit time (MTT) and capillary transit time (CTT). The ASL method was applied to measure the haemodynamic response in the primary somatosensory cortex following forepaw stimulation in the rat. Following stimulation an increase in signal intensity and rCBV(lw) was recorded, this was accompanied by a significant decrease in MTT (1.97+/-0.06s to 1.44+/-0.04s) and CTT (1.76+/-0.06s to 1.39+/-0.07s). Two animals were scanned repeatedly on two different experimental days. Stimulation in the first animal was applied to the same forepaw during the initial and repeat scan. In the second animal stimulation was applied to different forepaws on the first and second days. The control and activated ASL signal intensities, rCBVlw on both days were almost identical in both animals. The basal MTT and CTT during the second scan were also very similar to the values obtained during the first scan. The MTT recorded from the animal that underwent stimulation to the same paw during both scanning sessions was very similar on the first and second days. In conclusion, propofol induces little physiological disturbance and holds potential for longitudinal QASL fMRI studies.
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