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Ditz C, Leppert J, Küchler J. In Response: Volatile Sedation with Sevoflurane After Aneurysmal Subarachnoid Hemorrhage Using the Sedaconda Anesthetic Conserving Device: Is It Safe? Neurocrit Care 2024; 41:312-313. [PMID: 38902583 DOI: 10.1007/s12028-024-02034-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2024] [Accepted: 06/05/2024] [Indexed: 06/22/2024]
Affiliation(s)
- Claudia Ditz
- Department of Neurosurgery, University Hospital of Schleswig-Holstein, Campus Lübeck, Ratzeburger Allee 160, Lübeck, Germany.
| | - Jan Leppert
- Department of Neurosurgery, University Hospital of Schleswig-Holstein, Campus Lübeck, Ratzeburger Allee 160, Lübeck, Germany
| | - Jan Küchler
- Department of Neurosurgery, University Hospital of Schleswig-Holstein, Campus Lübeck, Ratzeburger Allee 160, Lübeck, Germany
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Keilholz SD, Pan WJ, Billings J, Nezafati M, Shakil S. Noise and non-neuronal contributions to the BOLD signal: applications to and insights from animal studies. Neuroimage 2016; 154:267-281. [PMID: 28017922 DOI: 10.1016/j.neuroimage.2016.12.019] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Revised: 10/21/2016] [Accepted: 12/08/2016] [Indexed: 01/08/2023] Open
Abstract
The BOLD signal reflects hemodynamic events within the brain, which in turn are driven by metabolic changes and neural activity. However, the link between BOLD changes and neural activity is indirect and can be influenced by a number of non-neuronal processes. Motion and physiological cycles have long been known to affect the BOLD signal and are present in both humans and animal models. Differences in physiological baseline can also contribute to intra- and inter-subject variability. The use of anesthesia, common in animal studies, alters neural activity, vascular tone, and neurovascular coupling. Most intriguing, perhaps, are the contributions from other processes that do not appear to be neural in origin but which may provide information about other aspects of neurophysiology. This review discusses different types of noise and non-neuronal contributors to the BOLD signal, sources of variability for animal studies, and insights to be gained from animal models.
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Affiliation(s)
- Shella D Keilholz
- Wallace H. Coulter Department of Biomedical Engineering, Emory University/Georgia Institute of Technology, Atlanta, GA, United States; Neuroscience Program, Emory University, Atlanta, GA, United States.
| | - Wen-Ju Pan
- Wallace H. Coulter Department of Biomedical Engineering, Emory University/Georgia Institute of Technology, Atlanta, GA, United States
| | - Jacob Billings
- Neuroscience Program, Emory University, Atlanta, GA, United States
| | - Maysam Nezafati
- Wallace H. Coulter Department of Biomedical Engineering, Emory University/Georgia Institute of Technology, Atlanta, GA, United States
| | - Sadia Shakil
- Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA, United States
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Lyons DG, Parpaleix A, Roche M, Charpak S. Mapping oxygen concentration in the awake mouse brain. eLife 2016; 5. [PMID: 26836304 PMCID: PMC4775210 DOI: 10.7554/elife.12024] [Citation(s) in RCA: 97] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Accepted: 01/25/2016] [Indexed: 01/16/2023] Open
Abstract
Although critical for brain function, the physiological values of cerebral oxygen concentration have remained elusive because high-resolution measurements have only been performed during anesthesia, which affects two major parameters modulating tissue oxygenation: neuronal activity and blood flow. Using measurements of capillary erythrocyte-associated transients, fluctuations of oxygen partial pressure (Po2) associated with individual erythrocytes, to infer Po2 in the nearby neuropil, we report the first non-invasive micron-scale mapping of cerebral Po2 in awake, resting mice. Interstitial Po2 has similar values in the olfactory bulb glomerular layer and the somatosensory cortex, whereas there are large capillary hematocrit and erythrocyte flux differences. Awake tissue Po2 is about half that under isoflurane anesthesia, and within the cortex, vascular and interstitial Po2 values display layer-specific differences which dramatically contrast with those recorded under anesthesia. Our findings emphasize the importance of measuring energy parameters non-invasively in physiological conditions to precisely quantify and model brain metabolism. DOI:http://dx.doi.org/10.7554/eLife.12024.001 Brain cells need a constant supply of oxygen to fuel their activities. This oxygen is delivered by the flow of blood through the vessels in the brain. If the blood flow to brain tissue is cut off as happens in stroke, or if an individual stops breathing, the brain becomes deprived of oxygen and brain cells will be damaged and die. To better understand how the brain works in health and disease, scientists need to learn how much oxygen the blood must deliver to the brain tissue to adequately support the activities of brain cells. Many studies have measured oxygen levels in the brain. However, these studies have looked only roughly and taken measurements from large areas of the brain, or they have involved animals receiving anesthesia, which can alter blood flow and oxygen use in the brain. Recently, scientists discovered that they could measure oxygen concentration at high detail in the brain of anesthetized rodents with a specialized microscope, by using molecules that emit light at a rate that depends on the local oxygen concentration. Now, Lyons et al. have shown that this same technique can be used in mice that are awake. First, a piece of the skull was replaced with glass to create a small transparent window. Then, the animals were allowed to recover for a few weeks, and were trained to get them used to how they would be handled during the experiments. After this period, the oxygen concentrations and blood flow in different parts of the mouse brains were measured in fine detail using the microscope while the animals were awake and relaxed. The experiments showed that oxygen levels in awake resting mice are actually lower than in anesthetized mice, and that oxygen levels differ between different parts of the mouse brain. This first detailed look at oxygen levels in the brain of awake animals will likely lead to more studies. For example, future studies may look at how quickly the brain uses oxygen under normal conditions and what happens in the brain during disease. DOI:http://dx.doi.org/10.7554/eLife.12024.002
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Affiliation(s)
- Declan G Lyons
- Institut National de la Santé et de la Recherche Médicale, U1128, Paris, France.,Laboratory of Neurophysiology and New Microscopies, Université Paris Descartes, Paris, France
| | - Alexandre Parpaleix
- Institut National de la Santé et de la Recherche Médicale, U1128, Paris, France.,Laboratory of Neurophysiology and New Microscopies, Université Paris Descartes, Paris, France
| | - Morgane Roche
- Institut National de la Santé et de la Recherche Médicale, U1128, Paris, France.,Laboratory of Neurophysiology and New Microscopies, Université Paris Descartes, Paris, France
| | - Serge Charpak
- Institut National de la Santé et de la Recherche Médicale, U1128, Paris, France.,Laboratory of Neurophysiology and New Microscopies, Université Paris Descartes, Paris, France
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Pan WJ, Billings JCW, Grooms JK, Shakil S, Keilholz SD. Considerations for resting state functional MRI and functional connectivity studies in rodents. Front Neurosci 2015; 9:269. [PMID: 26300718 PMCID: PMC4525377 DOI: 10.3389/fnins.2015.00269] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Accepted: 07/16/2015] [Indexed: 12/31/2022] Open
Abstract
Resting state functional MRI (rs-fMRI) and functional connectivity mapping have become widely used tools in the human neuroimaging community and their use is rapidly spreading into the realm of rodent research as well. One of the many attractive features of rs-fMRI is that it is readily translatable from humans to animals and back again. Changes in functional connectivity observed in human studies can be followed by more invasive animal experiments to determine the neurophysiological basis for the alterations, while exploratory work in animal models can identify possible biomarkers for further investigation in human studies. These types of interwoven human and animal experiments have a potentially large impact on neuroscience and clinical practice. However, impediments exist to the optimal application of rs-fMRI in small animals, some similar to those encountered in humans and some quite different. In this review we identify the most prominent of these barriers, discuss differences between rs-fMRI in rodents and in humans, highlight best practices for animal studies, and review selected applications of rs-fMRI in rodents. Our goal is to facilitate the integration of human and animal work to the benefit of both fields.
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Affiliation(s)
- Wen-Ju Pan
- Department of Biomedical Engineering, Georgia Institute of Technology, Emory University Atlanta, GA, USA
| | | | - Joshua K Grooms
- Department of Biomedical Engineering, Georgia Institute of Technology, Emory University Atlanta, GA, USA
| | - Sadia Shakil
- School of Electrical and Computer Engineering, Georgia Institute of Technology Atlanta, GA, USA
| | - Shella D Keilholz
- Department of Biomedical Engineering, Georgia Institute of Technology, Emory University Atlanta, GA, USA ; Neuroscience Program, Emory University Atlanta, GA, USA
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Normal cerebral FDG uptake during childhood. Eur J Nucl Med Mol Imaging 2013; 41:723-35. [PMID: 24323306 DOI: 10.1007/s00259-013-2639-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2013] [Accepted: 11/12/2013] [Indexed: 01/03/2023]
Abstract
PURPOSE Current understanding of cerebral FDG uptake during childhood originates from a small number of studies in patients with neurological abnormalities. Our aim was to describe cerebral FDG uptake in a dataset of FDG PET scans in children more likely to represent a normal population. METHODS We reviewed cerebral FDG PET scans in children up to 16 years of age with suspected/proven extracranial malignancies and the following exclusions: central nervous system metastases, previous malignancies, previous chemotherapy or radiotherapy, development of cerebral metastases during therapy, neurological conditions, taking antiepileptic medication or medications likely to interfere with cerebral metabolism, and general anaesthesia within 24 h. White matter, basal ganglia, thalamus and the cerebellar cortex were analysed using regional SUV(max), and the cerebral cortex, basal ganglia, thalamus and cerebellum were analysed using a regional relative uptake analysis in comparison to maximal cortical uptake. RESULTS Scans from 30 patients (age range 11 months to 16 years, mean age 10 years 5 months) were included. All regions showed increasing SUV(max) with age. The parietal, occipital, lateral temporal and medial temporal lobes showed lower rates of increasing FDG uptake causing changing patterns of regional FDG uptake during childhood. The cortical regions showing the most intense uptake in early childhood were the parietal and occipital lobes. At approximately 7 years of age these regions had relatively less uptake than the frontal lobes and at approximately 10 years of age these regions had relatively less uptake than the thalamus. CONCLUSION Relative FDG uptake in the brain has not reached an adult pattern by 1 year of age, but continues to change up to 16 years of age. The changing pattern is due to different regional rates of increasing cortical FDG uptake, which is less rapid in the parietal, occipital and temporal lobes than in the frontal lobes.
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Razoux F, Baltes C, Mueggler T, Seuwen A, Russig H, Mansuy I, Rudin M. Functional MRI to assess alterations of functional networks in response to pharmacological or genetic manipulations of the serotonergic system in mice. Neuroimage 2013; 74:326-36. [DOI: 10.1016/j.neuroimage.2013.02.031] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2012] [Revised: 01/17/2013] [Accepted: 02/11/2013] [Indexed: 01/21/2023] Open
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Villa F, Iacca C, Molinari AF, Giussani C, Aletti G, Pesenti A, Citerio G. Inhalation versus endovenous sedation in subarachnoid hemorrhage patients: effects on regional cerebral blood flow. Crit Care Med 2012; 40:2797-804. [PMID: 22824929 DOI: 10.1097/ccm.0b013e31825b8bc6] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE Isoflurane is a volatile anesthetic that has a vasodilating effect on cerebral vessels producing a cerebral blood flow increase. Furthermore, it has been shown in animal studies that isoflurane, when used as a preconditioning agent, has neuroprotective properties, inducing tolerance to ischemia. However, it is not routinely used in neurointensive care because of the potential increase in intracranial pressure caused by the rise in cerebral blood flow. Nevertheless, subarachnoid hemorrhage patients who are at risk for vasospasm may benefit from an increase in cerebral blood flow. We measured regional cerebral blood flow during intravenous sedation with propofol and during sedation with isoflurane in patients with severe subarachnoid hemorrhage not having intracranial hypertension. DESIGN The study is a crossover, open clinical trial (NCT00830843). SETTING Neurointensive care unit of an academic hospital. PATIENTS Thirteen patients with severe subarachnoid hemorrhage, (median Fisher scale 4), monitored on clinical indication with intracranial pressure device and a thermal diffusion probe for the assessment of regional cerebral blood flow. An intracranial pressure>18 mm Hg was an exclusion criterion. INTERVENTIONS Cerebral and hemodynamic variables were assessed at three steps. Step 1: sedation with propofol 3-4 mg/kg/hr; step 2: after 1 hr of propofol discontinuation and isoflurane 0.8%; step 3: after 1 hr of propofol at the same previous infusion rate. Cerebral perfusion pressure and arterial PCO2 were maintained constant. Mean cerebral artery flow velocity and jugular vein oxygen saturation were measured at the end of each step. MEASUREMENTS AND MAIN RESULTS Regional cerebral blood flow increased significantly during step 2 (39.3±29 mL/100 hg/min) compared to step 1 (20.8±10.7) and step 3 (24.7±8). There was no difference in regional cerebral blood flow comparing step 1 vs. step 3. No significant difference in intracranial pressure, mean cerebral artery transcranial Doppler velocity, PaCO2, cerebral perfusion pressure between the different steps. CONCLUSIONS Isoflurane increases regional cerebral blood flow in comparison to propofol. Intracranial pressure did not change significantly in the population not affected by intracranial hypertension.
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Affiliation(s)
- Federico Villa
- Division of NeuroIntensive Care, Department of Anesthesia and Critical Care, Ospedale San Gerardo, Monza, Italy.
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Pierleoni F, Gizdulich A, Paoletti F. The influence of ULF-TENS on electroencephalographic tracings. Cranio 2011; 29:38-42. [PMID: 21370768 DOI: 10.1179/crn.2011.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
The purpose of this study was to evaluate and quantify the effects of Ultra-Low Frequency Transcutaneous Electrical Nerve Stimulation (ULF-TENS) on the Central Nervous System, using electroencephalography. The research was conducted on a study group of twelve patients, and a control group of six. Patients were chosen between the ages of twenty and thirty years old, and all had occlusal flags without pain. The electroencephalography patterns were registered, for each patient in the study group, before and after the application of 60' of the ULF-TENS. In nine of the twelve cases studied, a diminution of the cerebral rhythm was registered along with the appearance of a sedative effect caused by an increment in Alfa waves and a state of hypo-alertness caused by an increment in the theta rhythm. An identical effect was registered in one subject of the control group while another subject had an increased cerebral rhythm, and in the remaining four subjects, all values remained invariable. The study demonstrated two important points. First, it confirmed the utility of the EEG as a noninvasive useful method in order to study the central effects of the ULF-TENS, and second, also positive, it revealed the sedative effects on the central nervous system registered by the EEG.
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Affiliation(s)
- Felicita Pierleoni
- Dept. of Stomatology, University of Florence, Via del Ponte Di Mezzo 46-48, Florence 50100, Italy.
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Noirhomme Q, Soddu A, Lehembre R, Vanhaudenhuyse A, Boveroux P, Boly M, Laureys S. Brain connectivity in pathological and pharmacological coma. Front Syst Neurosci 2010; 4:160. [PMID: 21191476 PMCID: PMC3010745 DOI: 10.3389/fnsys.2010.00160] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2010] [Accepted: 12/07/2010] [Indexed: 12/28/2022] Open
Abstract
Recent studies in patients with disorders of consciousness (DOC) tend to support the view that awareness is not related to activity in a single brain region but to thalamo-cortical connectivity in the frontoparietal network. Functional neuroimaging studies have shown preserved albeit disconnected low-level cortical activation in response to external stimulation in patients in a "vegetative state" or unresponsive wakefulness syndrome. While activation of these "primary" sensory cortices does not necessarily reflect conscious awareness, activation in higher-order associative cortices in minimally conscious state patients seems to herald some residual perceptual awareness. PET studies have identified a metabolic dysfunction in a widespread frontoparietal "global neuronal workspace" in DOC patients including the midline default mode network ("intrinsic" system) and the lateral frontoparietal cortices or "extrinsic system." Recent studies have investigated the relation of awareness to the functional connectivity within intrinsic and extrinsic networks, and with the thalami in both pathological and pharmacological coma. In brain damaged patients, connectivity in all default network areas was found to be non-linearly correlated with the degree of clinical consciousness impairment, ranging from healthy controls and locked-in syndrome to minimally conscious, vegetative, coma, and brain dead patients. Anesthesia-induced loss of consciousness was also shown to correlate with a global decrease in cortico-cortical and thalamo-cortical connectivity in both intrinsic and extrinsic networks, but not in auditory, or visual networks. In anesthesia, unconsciousness was also associated with a loss of cross-modal interactions between networks. These results suggest that conscious awareness critically depends on the functional integrity of thalamo-cortical and cortico-cortical frontoparietal connectivity within and between "intrinsic" and "extrinsic" brain networks.
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Affiliation(s)
- Quentin Noirhomme
- Coma Science Group, Cyclotron Research Centre and Neurology Department, University and University Hospital of LiègeLiège, Belgium
| | - Andrea Soddu
- Coma Science Group, Cyclotron Research Centre and Neurology Department, University and University Hospital of LiègeLiège, Belgium
| | - Rémy Lehembre
- Coma Science Group, Cyclotron Research Centre and Neurology Department, University and University Hospital of LiègeLiège, Belgium
- Communications and Remote Sensing Laboratory, School of Engineering, Université Catholique de LouvainLouvain-la-Neuve, Belgium
| | - Audrey Vanhaudenhuyse
- Coma Science Group, Cyclotron Research Centre and Neurology Department, University and University Hospital of LiègeLiège, Belgium
| | - Pierre Boveroux
- Coma Science Group, Cyclotron Research Centre and Neurology Department, University and University Hospital of LiègeLiège, Belgium
- Department of Anesthesiology, University Hospital of LiègeLiège, Belgium
| | - Mélanie Boly
- Coma Science Group, Cyclotron Research Centre and Neurology Department, University and University Hospital of LiègeLiège, Belgium
| | - Steven Laureys
- Coma Science Group, Cyclotron Research Centre and Neurology Department, University and University Hospital of LiègeLiège, Belgium
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Zhao F, Fan X, Grondin R, Edwards R, Forman E, Moorehead J, Gerhardt G, Wang X, Zhang Z. Improved methods for electroacupuncture and electromyographic recordings in normal and parkinsonian rhesus monkeys. J Neurosci Methods 2010; 192:199-206. [PMID: 20654649 DOI: 10.1016/j.jneumeth.2010.07.016] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2010] [Revised: 07/13/2010] [Accepted: 07/14/2010] [Indexed: 12/22/2022]
Abstract
Although acupuncture has been widely and routinely used in healthcare in the USA, its use has been based more on empirical observation than on scientific knowledge. Therefore, there is a great need for better understanding the underlying mechanism(s) of action. A great body of evidence supports that nonhuman primates are a candidate for studying human diseases. However, the use of nonhuman primates in neurophysiological, neuroimaging and neurochemical studies is extremely challenging, especially under fully conscious, alert conditions. In the present study, we developed a protocol for safely performing acupuncture, electroacupuncture (EA) and electromyography (EMG) in both normal nonhuman primates and animals with parkinsonian-like symptoms. Four normal and four hemiparkinsonian middle-aged rhesus monkeys were extensively trained, behaviorally monitored, and received both EA and EMG for several months. The results demonstrated that (1) all rhesus monkeys used in the study could be trained for procedures including EA and EMG; (2) all animals tolerated the procedures involving needle/electrode insertion; (3) EA procedures used in the study did not adversely alter the animal's locomotor activities; rather, MPTP-treated animals showed a significant improvement in movement speed; and (4) EMG detected significant differences in muscle activity between the arms with and without MPTP-induced rigidity. Our results support that rhesus monkeys can be used as an experimental animal model to study EA and that EMG has the potential to be used to objectively assess the effects of antiparkinsonian therapies. The results also indicate that animals, especially those with parkinsonian-like symptoms, could benefit from long-term EA stimulations.
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Affiliation(s)
- Feng Zhao
- Department of Physiology, Key Laboratory for Neurodegenerative Disorders of the Ministry Education, Capital Medical University, Beijing 100069, PR China
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Casteels C, Bormans G, Van Laere K. The effect of anaesthesia on [(18)F]MK-9470 binding to the type 1 cannabinoid receptor in the rat brain. Eur J Nucl Med Mol Imaging 2010; 37:1164-73. [PMID: 20182714 DOI: 10.1007/s00259-010-1383-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2009] [Accepted: 01/05/2010] [Indexed: 11/27/2022]
Abstract
PURPOSE Small animal PET can be applied to study molecular processes in animal models of a variety of human diseases. In order to keep the animals in a restricted position during imaging, anaesthesia is in many instances inevitable. Using small animal PET and ex vivo autoradiography, we examined the influence of pentobarbital and isoflurane anaesthesia on the rat brain uptake of [(18)F]MK-9470, a radioligand for the type 1 cannabinoid receptor. METHODS PET imaging was performed on adult Wistar rats under pentobarbital (n = 6) and isoflurane anaesthesia (n = 7), and under control conditions (free moving during tracer uptake, n = 8). Parametric PET images were generated, anatomically standardized and analysed by voxel-based Statistical Parametric Mapping and a predefined volume of interest approach. Immediately after in vivo PET, brains were processed for ex vivo autoradiography using manually placed regions of interest. An extra group (n = 6) was included ex vivo, in which animals were intravenously injected without the use of anaesthetics. RESULTS Using in vivo and ex vivo molecular imaging techniques, no significant changes in absolute [(18)F]MK-9470 uptake were present in the brain of pentobarbital and isoflurane rats as compared to control conditions. Relative [(18)F]MK-9470 uptake PET values obtained applying global scaling were, however, decreased in the cortex under both anaesthetics (pentobarbital: -13.3+/-1.4%; isoflurane -8.7 +/- 3.1%), while an increase was seen in the cerebellum by 13.5 +/- 4.0% and 13.9 +/- 4.1% under pentobarbital and isoflurane, respectively. Ex vivo results were in agreement with in vivo findings. CONCLUSION These findings suggest a similar, regionally specific interference of pentobarbital and isoflurane anaesthesia with in vivo CB1 receptor imaging using [(18)F]MK-9470.
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Affiliation(s)
- Cindy Casteels
- Division of Nuclear Medicine, KU Leuven and University Hospital Gasthuisberg, Herestraat 49 bus 7003, 3000, Leuven, Belgium.
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Harris AD, Kosior RK, Chen HS, Andersen LB, Frayne R. Evolution of hyperacute stroke over 6 hours using serial MR perfusion and diffusion maps. J Magn Reson Imaging 2009; 29:1262-70. [PMID: 19472379 DOI: 10.1002/jmri.21763] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
PURPOSE To develop an appropriate method to evaluate the time-course of diffusion and perfusion changes in a clinically relevant animal model of ischemic stroke and to examine lesion progression on MR images. An exploration of acute stroke infarct expansion was performed in this study by using a new methodology for developing time-to-infarct maps based on the time at which each voxel becomes infarcted. This enabled definition of homogeneous regions from the heterogeneous stroke infarct. MATERIALS AND METHODS Time-to-infarct maps were developed based on apparent diffusion coefficient (ADC) changes. These maps were validated and then applied to blood flow and time-to-peak maps to examine perfusion changes. RESULTS ADC stroke infarct showed different evolution patterns depending on the time at which that region of tissue infarcted. Applying the time-to-infarct maps to the perfusion maps showed localized perfusion evolution characteristics. In some regions, perfusion was immediately affected and showed little change over the experiment; however, in some regions perfusion changes were more dynamic. CONCLUSION Results were consistent with the diffusion-perfusion mismatch hypothesis. In addition, characteristics of collateral recruitment were identified, which has interesting stroke pathophysiology and treatment implications.
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Affiliation(s)
- Ashley D Harris
- Seaman Family MR Research Centre, Foothills Medical Centre, University of Calgary, Alberta, Canada
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Martuzzi R, Ramani R, Qiu M, Rajeevan N, Constable RT. Functional connectivity and alterations in baseline brain state in humans. Neuroimage 2009; 49:823-34. [PMID: 19631277 DOI: 10.1016/j.neuroimage.2009.07.028] [Citation(s) in RCA: 151] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2009] [Revised: 07/10/2009] [Accepted: 07/15/2009] [Indexed: 11/18/2022] Open
Abstract
This work examines the influence of changes in baseline activity on the intrinsic functional connectivity fMRI (fc-fMRI) in humans. Baseline brain activity was altered by inducing anesthesia (sevoflurane end-tidal concentration 1%) in human volunteers and fc-fMRI maps between the pre-anesthetized and anesthetized conditions were compared across different brain networks. We particularly focused on low-level sensory areas (primary somatosensory, visual, and auditory cortices), the thalamus, and pain (insula), memory (hippocampus) circuits, and the default mode network (DMN), the latter three to examine higher-order brain regions. The results indicate that, while fc-fMRI patterns did not significantly differ (p<0.005; 20-voxel cluster threshold) in sensory cortex and in the DMN between the pre- and anesthetized conditions, fc-fMRI in high-order cognitive regions (i.e. memory and pain circuits) was significantly altered by anesthesia. These findings provide further evidence that fc-fMRI reflects intrinsic brain properties, while also demonstrating that 0.5 MAC sevoflurane anesthesia preferentially modulates higher-order connections.
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Affiliation(s)
- Roberto Martuzzi
- Department of Diagnostic Radiology, Yale University School of Medicine, The Anlyan Center, 300 Cedar Street, New Haven, CT 06520-8042, USA.
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