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Lindh E, Meller A, Raekallio M. Effects of vatinoxan in rats sedated with a combination of medetomidine, midazolam and fentanyl. Acta Vet Scand 2024; 66:23. [PMID: 38822394 PMCID: PMC11141047 DOI: 10.1186/s13028-024-00744-y] [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: 12/19/2023] [Accepted: 05/22/2024] [Indexed: 06/03/2024] Open
Abstract
BACKGROUND Alpha2-adrenoceptor agonists (α2-agonists) are widely used in animals as sedatives and for pre-anaesthetic medication. Medetomidine has often been given subcutaneously (SC) to rats, although its absorption rate is slow and the individual variation in serum drug concentrations is high via this route. In addition, α2-agonists have various effects on metabolic and endocrine functions such as hypoinsulinaemia, hyperglycaemia and diuresis. Vatinoxan is a peripherally acting α2-adrenoceptor antagonist that, as a hydrophilic molecule, does not cross the blood-brain barrier in significant quantities and thus alleviates peripheral cardiovascular effects and adverse metabolic effects of α2-agonists. Aim of this study was to evaluate the effects of vatinoxan on sedation, blood glucose concentration, voiding and heart and respiratory rates and arterial oxygen saturation in rats sedated with subcutaneous medetomidine, midazolam and fentanyl. RESULTS Onset of sedation and loss of righting reflex occurred significantly faster with vatinoxan [5.35 ± 1.08 (mean ± SD) versus 12.97 ± 6.18 min and 6.53 ± 2.18 versus 14.47 ± 7.28 min, respectively]. No significant differences were detected in heart and respiratory rates and arterial oxygen saturation between treatments. Blood glucose concentration (18.3 ± 3.6 versus 11.8 ± 1.2 mmol/L) and spontaneous urinary voiding [35.9 (15.1-41.6), range (median) versus 0.9 (0-8.0) mL /kg/min] were significantly higher without vatinoxan. CONCLUSIONS Acceleration of induction of sedation, alleviation of hyperglycaemia and prevention of profuse diuresis by vatinoxan may be beneficial when sedating rats for clinical and experimental purposes with subcutaneous medetomidine, midazolam and fentanyl.
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Affiliation(s)
- Emily Lindh
- Department of Equine and Small Animal Medicine, Faculty of Veterinary Medicine, University of Helsinki, Koetilantie 4, P.O.Box 57, Helsinki, FI-00014, Finland
| | - Anna Meller
- Laboratory Animal Center, Mustialankatu 1 G, P.O.Box 29, Helsinki, FI-00014, Finland
| | - Marja Raekallio
- Department of Equine and Small Animal Medicine, Faculty of Veterinary Medicine, University of Helsinki, Koetilantie 4, P.O.Box 57, Helsinki, FI-00014, Finland.
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2
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Xie Z, Fox AP. Rapid emergence from dexmedetomidine sedation in Sprague Dawley rats by repurposing an α 2-adrenergic receptor competitive antagonist in combination with caffeine. BMC Anesthesiol 2023; 23:39. [PMID: 36721095 PMCID: PMC9890710 DOI: 10.1186/s12871-023-01986-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Accepted: 01/16/2023] [Indexed: 02/02/2023] Open
Abstract
BACKGROUND The α2 adrenergic receptor agonist dexmedetomidine is an important intravenous sedative with analgesic properties. Currently available dexmedetomidine reversal agents, like the α2-receptor antagonist atipamezole, cause serious adverse effects at the large dosages required for effective reversal; they are not used clinically. Without reversal agents, emergence times from dexmedetomidine sedation are slow. In this study we tested the ability of low-dose atipamezole, in combination with caffeine, to reverse dexmedetomidine sedation. The low dose of atipamezole employed should not be associated with unwanted effects. METHODS Two different sedation protocols were employed. In the first protocol, a bolus of dexmedetomidine was rapidly applied and the drug was allowed to equilibrate for 10 min before rats received either saline (as control) or low-dose atipamezole with caffeine. Following this procedure, rats were placed on their backs. Emergence from sedation was the time for rats to recover their righting reflex and stand with 4 paws on the floor. A second sedation protocol simulated a pediatric magnetic resonance imaging (MRI) scan. Adult rats were sedated with dexmedetomidine for one hour followed by 30 min with both dexmedetomidine and propofol. At the end of 90 min, rats received either saline (control) or a combination of low-dose atipamezole, and caffeine. Recovery of the righting reflex was used as a proxy for emergence from sedation. RESULTS Emergence from sedation, the time for rats to recover their righting reflex, decreased by ~ 90% when using an atipamezole dose ~ 20 fold lower than manufacturer's recommendation, supplemented with caffeine. Using an atipamezole dose ~ tenfold lower than recommended, with caffeine, emergence times decreased by ~ 97%. A different stimulant, forskolin, when tested, was as effective as caffeine. For the MRI simulation, emergence times were decreased by ~ 93% by low-dose atipamezole with caffeine. CONCLUSIONS Low dose atipamezole with caffeine was effective at reversing dexmedetomidine sedation. Emergence was rapid and the rats regained not only their righting reflex but also their balance and their ability to carry out complex behaviors. These findings suggest that the combination of low dose atipamezole with caffeine may permit rapid clinical reversal of dexmedetomidine without unwanted effects.
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Affiliation(s)
- Zheng Xie
- Department of Anesthesia and Critical Care, The University of Chicago, Chicago, IL, USA
| | - Aaron P Fox
- Department of Neurobiology, Pharmacology and Physiology, The University of Chicago, Chicago, IL, USA.
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3
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Lambers H, Wachsmuth L, Lippe C, Faber C. The impact of vasomotion on analysis of rodent fMRI data. Front Neurosci 2023; 17:1064000. [PMID: 36908777 PMCID: PMC9998505 DOI: 10.3389/fnins.2023.1064000] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Accepted: 02/06/2023] [Indexed: 03/14/2023] Open
Abstract
Introduction Small animal fMRI is an essential part of translational research in the cognitive neurosciences. Due to small dimensions and animal physiology preclinical fMRI is prone to artifacts that may lead to misinterpretation of the data. To reach unbiased translational conclusions, it is, therefore, crucial to identify potential sources of experimental noise and to develop correction methods for contributions that cannot be avoided such as physiological noise. Aim of this study was to assess origin and prevalence of hemodynamic oscillations (HDO) in preclinical fMRI in rat, as well as their impact on data analysis. Methods Following the development of algorithms for HDO detection and suppression, HDO prevalence in fMRI measurements was investigated for different anesthetic regimens, comprising isoflurane and medetomidine, and for both gradient echo and spin echo fMRI sequences. In addition to assessing the effect of vasodilation on HDO, it was studied if HDO have a direct neuronal correlate using local field potential (LFP) recordings. Finally, the impact of HDO on analysis of fMRI data was assessed, studying both the impact on calculation of activation maps as well as the impact on brain network analysis. Overall, 303 fMRI measurements and 32 LFP recordings were performed in 71 rats. Results In total, 62% of the fMRI measurements showed HDO with a frequency of (0.20 ± 0.02) Hz. This frequent occurrence indicated that HDO cannot be generally neglected in fMRI experiments. Using the developed algorithms, HDO were detected with a specificity of 95%, and removed efficiently from the signal time courses. HDO occurred brain-wide under vasoconstrictive conditions in both small and large blood vessels. Vasodilation immediately interrupted HDO, which, however, returned within 1 h under vasoconstrictive conditions. No direct neuronal correlate of HDO was observed in LFP recordings. HDO significantly impacted analysis of fMRI data, leading to altered cluster sizes and F-values for activated voxels, as well as altered brain networks, when comparing data with and without HDO. Discussion We therefore conclude that HDO are caused by vasomotion under certain anesthetic conditions and should be corrected during fMRI data analysis to avoid bias.
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Affiliation(s)
| | - Lydia Wachsmuth
- Clinic of Radiology, University of Münster, Münster, Germany
| | - Chris Lippe
- Clinic of Radiology, University of Münster, Münster, Germany
| | - Cornelius Faber
- Clinic of Radiology, University of Münster, Münster, Germany
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Ferris CF. Applications in Awake Animal Magnetic Resonance Imaging. Front Neurosci 2022; 16:854377. [PMID: 35450017 PMCID: PMC9017993 DOI: 10.3389/fnins.2022.854377] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Accepted: 03/09/2022] [Indexed: 12/16/2022] Open
Abstract
There are numerous publications on methods and applications for awake functional MRI across different species, e.g., voles, rabbits, cats, dogs, and rhesus macaques. Each of these species, most obviously rhesus monkey, have general or unique attributes that provide a better understanding of the human condition. However, much of the work today is done on rodents. The growing number of small bore (≤30 cm) high field systems 7T- 11.7T favor the use of small animals. To that point, this review is primarily focused on rodents and their many applications in awake function MRI. Applications include, pharmacological MRI, drugs of abuse, sensory evoked stimuli, brain disorders, pain, social behavior, and fear.
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Abstract
Sedation and anesthesia in rodent species are complex due to their wide species variation, small size, and metabolism. This review article covers recent advances in sedation and anesthesia as well as an updated drug formulary for sedation protocols. Setup, equipment, monitoring, maintenance, and recovery are reviewed as well as species-specific anatomy.
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Affiliation(s)
- Katarina Bennett
- Avian & Exotics Service, Bluepearl Emergency and Specialty Hospital, 7414 S Tamiami Trl. Sarasota, FL 34231, USA.
| | - Kerrie Lewis
- Pebble Creek Animal Hospital, 19440 Bruce B Downs Boulevard, Tampa, FL 33647, USA
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Pradier B, Wachsmuth L, Nagelmann N, Segelcke D, Kreitz S, Hess A, Pogatzki-Zahn EM, Faber C. Combined resting state-fMRI and calcium recordings show stable brain states for task-induced fMRI in mice under combined ISO/MED anesthesia. Neuroimage 2021; 245:118626. [PMID: 34637903 DOI: 10.1016/j.neuroimage.2021.118626] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Accepted: 09/27/2021] [Indexed: 11/28/2022] Open
Abstract
For fMRI in animal models, the combination of low-dose anesthetic, isoflurane (ISO), and the sedative medetomidine (MED) has recently become an advocated regimen to achieve stable neuronal states and brain networks in rats that are required for reliable task-induced BOLD fMRI. However, in mice the temporal stability of neuronal states and networks in resting-state (rs)-fMRI experiments during the combined ISO/MED regimen has not been systematically investigated. Using a multimodal approach with optical calcium (Ca2+) recordings and rs-fMRI, we investigated cortical neuronal/astrocytic Ca2+activity states and brain networks at multiple time points while switching from anesthesia with 1% ISO to a combined ISO/MED regimen. We found that cortical activity states reached a steady-state 45 min following start of MED infusion as indicated by stable Ca2+ transients. Similarly, rs-networks were not statistically different between anesthesia with ISO and the combined ISO/MED regimen 45 and 100 min after start of MED. Importantly, during the transition time we identified changed rs-network signatures that likely reflect the different mode of action of the respective anesthetic; these included a dose-dependent increase in cortico-cortical functional connectivity (FC) presumably caused by reduction of ISO concentration and decreased FC in subcortical arousal nuclei due to MED infusion. Furthermore, we report detection of visual stimulation-induced BOLD fMRI during the stable ISO/MED neuronal state 45 min after induction. Based on our findings, we recommend a 45-minute waiting period after switching from ISO anesthesia to the combined ISO/MED regimen before performing rs- or task-induced fMRI experiments.
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Affiliation(s)
- Bruno Pradier
- Department of Clinical Radiology, Translational Research Imaging Center, University Hospital Münster, Münster 48149, Germany; Department of Anesthesiology Intensive Care and Pain Medicine, University Hospital Münster, Germany
| | - Lydia Wachsmuth
- Department of Clinical Radiology, Translational Research Imaging Center, University Hospital Münster, Münster 48149, Germany
| | - Nina Nagelmann
- Department of Clinical Radiology, Translational Research Imaging Center, University Hospital Münster, Münster 48149, Germany
| | - Daniel Segelcke
- Department of Anesthesiology Intensive Care and Pain Medicine, University Hospital Münster, Germany
| | - Silke Kreitz
- Institute of Experimental and Clinical Pharmacology and Toxicology, Emil Fischer Center, University of Erlangen-Nuremberg, Erlangen, Germany
| | - Andreas Hess
- Institute of Experimental and Clinical Pharmacology and Toxicology, Emil Fischer Center, University of Erlangen-Nuremberg, Erlangen, Germany
| | - Esther M Pogatzki-Zahn
- Department of Anesthesiology Intensive Care and Pain Medicine, University Hospital Münster, Germany
| | - Cornelius Faber
- Department of Clinical Radiology, Translational Research Imaging Center, University Hospital Münster, Münster 48149, Germany.
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Impact of anesthesia on static and dynamic functional connectivity in mice. Neuroimage 2021; 241:118413. [PMID: 34293463 DOI: 10.1016/j.neuroimage.2021.118413] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Revised: 07/13/2021] [Accepted: 07/19/2021] [Indexed: 11/22/2022] Open
Abstract
A few studies have compared the static functional connectivity between awake and lightly anesthetized states in rodents by resting-state fMRI. However, impact of light anesthesia on static and dynamic fluctuations in functional connectivity has not been fully understood. Here, we developed a resting-state fMRI protocol to perform awake and anesthetized functional MRI in the same mice. Static functional connectivity showed a widespread decrease under light anesthesia, such as when under isoflurane or a mixture of isoflurane and medetomidine. Several interhemispheric and subcortical connections were key connections for anesthetized condition from awake state. Dynamic functional connectivity demonstrates the shift from frequent broad connections across the cortex, the hypothalamus, and the auditory-visual cortex to frequent local connections within the cortex only under light anesthesia compared with awake state. Fractional amplitude of low frequency fluctuation in the thalamic nuclei decreased under both anesthesia. These results indicate that typical anesthetics for functional MRI alters the spatiotemporal profile of the dynamic brain network in subcortical regions, including the thalamic nuclei and limbic system.
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Baligand C, Barret O, Tourais A, Pérot JB, Thenadey D, Petit F, Liot G, Gaillard MC, Flament J, Dhenain M, Valette J. Zero Echo Time 17O-MRI Reveals Decreased Cerebral Metabolic Rate of Oxygen Consumption in a Murine Model of Amyloidosis. Metabolites 2021; 11:metabo11050263. [PMID: 33922384 PMCID: PMC8145383 DOI: 10.3390/metabo11050263] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2021] [Revised: 04/16/2021] [Accepted: 04/20/2021] [Indexed: 11/16/2022] Open
Abstract
The cerebral metabolic rate of oxygen consumption (CMRO2) is a key metric to investigate the mechanisms involved in neurodegeneration in animal models and evaluate potential new therapies. CMRO2 can be measured by direct 17O magnetic resonance imaging (17O-MRI) of H217O signal changes during inhalation of 17O-labeled oxygen gas. In this study, we built a simple gas distribution system and used 3D zero echo time (ZTE-)MRI at 11.7 T to measure CMRO2 in the APPswe/PS1dE9 mouse model of amyloidosis. We found that CMRO2 was significantly lower in the APPswe/PS1dE9 brain than in wild-type at 12-14 months. We also estimated cerebral blood flow (CBF) from the post-inhalation washout curve and found no difference between groups. These results suggest that the lower CMRO2 observed in APPswe/PS1dE9 is likely due to metabolism impairment rather than to reduced blood flow. Analysis of the 17O-MRI data using different quantification models (linear and 3-phase model) showed that the choice of the model does not affect group comparison results. However, the simplified linear model significantly underestimated the absolute CMRO2 values compared to a 3-phase model. This may become of importance when combining several metabolic fluxes measurements to study neuro-metabolic coupling.
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Musk GC. Refinements to Animal Models for Biomedical Research. Animals (Basel) 2020; 10:ani10122425. [PMID: 33352864 PMCID: PMC7766876 DOI: 10.3390/ani10122425] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2020] [Revised: 12/15/2020] [Accepted: 12/16/2020] [Indexed: 02/07/2023] Open
Affiliation(s)
- Gabrielle C Musk
- Animal Care Services, University of Western Australia, Perth 6107, Australia
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10
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Tristão Pereira C, Diao Y, Yin T, da Silva AR, Lanz B, Pierzchala K, Poitry-Yamate C, Jelescu IO. Synchronous nonmonotonic changes in functional connectivity and white matter integrity in a rat model of sporadic Alzheimer's disease. Neuroimage 2020; 225:117498. [PMID: 33164858 DOI: 10.1016/j.neuroimage.2020.117498] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Revised: 09/16/2020] [Accepted: 10/18/2020] [Indexed: 12/17/2022] Open
Abstract
Brain glucose hypometabolism has been singled out as an important contributor and possibly main trigger to Alzheimer's disease (AD). Intracerebroventricular injections of streptozotocin (icv-STZ) cause brain glucose hypometabolism without systemic diabetes. Here, a first-time longitudinal study of brain glucose metabolism, functional connectivity and white matter microstructure was performed in icv-STZ rats using PET and MRI. Histological markers of pathology were tested at an advanced stage of disease. STZ rats exhibited altered functional connectivity and intra-axonal damage and demyelination in brain regions typical of AD, in a temporal pattern of acute injury, transient recovery/compensation and chronic degeneration. In the context of sustained glucose hypometabolism, these nonmonotonic trends - also reported in behavioral studies of this animal model as well as in human AD - suggest a compensatory mechanism, possibly recruiting ketone bodies, that allows a partial and temporary repair of brain structure and function. The early acute phase could thus become a valuable therapeutic window to strengthen the recovery phase and prevent or delay chronic degeneration, to be considered both in preclinical and clinical studies of AD. In conclusion, this work reveals the consequences of brain insulin resistance on structure and function, highlights signature nonmonotonic trajectories in their evolution and proposes potent MRI-derived biomarkers translatable to human AD and diabetic populations.
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Affiliation(s)
- Catarina Tristão Pereira
- Centre d'Imagerie Biomédicale, EPFL, Station 6, Lausanne 1015, Switzerland; Faculdade de Ciências da Universidade de Lisboa, Lisbon, Portugal
| | - Yujian Diao
- Centre d'Imagerie Biomédicale, EPFL, Station 6, Lausanne 1015, Switzerland; Laboratoire d'Imagerie Fonctionnelle et Métabolique, EPFL, Lausanne, Switzerland
| | - Ting Yin
- Centre d'Imagerie Biomédicale, EPFL, Station 6, Lausanne 1015, Switzerland
| | - Analina R da Silva
- Centre d'Imagerie Biomédicale, EPFL, Station 6, Lausanne 1015, Switzerland
| | - Bernard Lanz
- Laboratoire d'Imagerie Fonctionnelle et Métabolique, EPFL, Lausanne, Switzerland
| | | | | | - Ileana O Jelescu
- Centre d'Imagerie Biomédicale, EPFL, Station 6, Lausanne 1015, Switzerland.
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