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Activation in the auditory pathway of the gerbil studied with 18F-FDG PET: effects of anesthesia

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Abstract

Here, we present results from an 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) study in the Mongolian gerbil, a preferred animal model in auditory research. One major issue in preclinical nuclear imaging, as well as in most of the neurophysiological methods investigating auditory processing, is the need of anesthesia. We compared the usability of two types of anesthesia which are frequently employed in electrophysiology, ketamine/xylazine (KX), and fentanyl/midazolam/medetomidine (FMM), for valid measurements of auditory activation with 18F-FDG PET. Gerbils were placed in a sound-shielding box and injected with 18F-FDG. Two acoustic free-field conditions were used: (1) baseline (no stimulation, 25 dB background noise) and (2) 90 dB frequency-modulated tones (FM). After 40 min of 18F-FDG uptake, a 30 min acquisition was performed using a small animal PET/CT system. Blood glucose levels were measured after the uptake phase before scanning. Standardized uptake value ratios for relevant regions were determined after implementing image and volume of interest templates. Scans demonstrated a significantly higher uptake in the inferior colliculus with FM stimulation compared to baseline in awake subjects (+ 12%; p = 0.02) and with FMM anesthesia (+ 13%; p = 0.0012), but not with KX anesthesia. In non-auditory brain regions, no significant difference was detected. Blood glucose levels were significantly higher under KX compared to FMM anesthesia (17.29 ± 0.42 mmol/l vs. 14.30 ± 1.91 mmol/l; p = 0.024). These results suggest that valid 18F-FDG PET measurements of auditory activation comparable to electrophysiology can be obtained from gerbils during opioid-based anesthesia due to its limited effects on interfering blood glucose levels.

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Acknowledgements

This work was supported by a grant from the Deutsche Forschungsgemeinschaft (EXC 1077). We wish to thank Silvia Eilert, Alexander Kanwischer, and Petra Felsch for their support during the PET scans. We thank Dr. Pablo Bascuñana for his comments on a previous version of the manuscript.

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Correspondence to Georg Berding.

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The authors declare that they have no conflict of interest.

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All applicable international, national, and/or institutional guidelines for the care and use of animals were followed.

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Kessler, M., Mamach, M., Beutelmann, R. et al. Activation in the auditory pathway of the gerbil studied with 18F-FDG PET: effects of anesthesia. Brain Struct Funct 223, 4293–4305 (2018). https://doi.org/10.1007/s00429-018-1743-9

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  • DOI: https://doi.org/10.1007/s00429-018-1743-9

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