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Lookup NU author(s): Dr Jasmine ClarksonORCiD, Dr Ross MuersORCiD, Dr Matthew Leach, Dr Jessica MartinORCiD
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
The ability to understand an animal’s capacity to experience negative sensations, such as pain and distress, during impaired states of consciousness is important for a wide variety of situations, and particularly when animals are being killed. Mice remain the predominant species used for scientific research globally, where a prerequisite requires them to be humanely killed at the end of the scientific work. However, the ability of some existing practices and methodologies to provide these animals with a humane death have been questioned (e.g. exposure to a rising concentration of carbon dioxide), thus requiring the development of novel, refined methodologies. We highlight the potential of hypobaric hypoxia to provide a humane alternative to hypercapnic hypoxia by combining behavioural with neurophysiological assessment (using electroencephalography, EEG) to characterise brain activity during the induction of unconsciousness. We demonstrate different patterns of brain activity between hypobaric and hypercapnic hypoxia, suggestive of key mechanistic differences in the transition towards unconsciousness. Unlike hypercapnic hypoxia, hypobaric hypoxia resulted in an early shift in peak power to lower delta frequency bands (<4Hz), suggestive of early cognitive impairment and an anaesthetic-like state before loss of posture. As such, mice are likely to have a reduced capacity to experience negative sensations such as distress and anxiety. Hypobaric hypoxia could provide the basis for major refinement to essential killing practices for laboratory mice worldwide.
Author(s): Clarkson JM, McKeegan DEF, Muers RS, Leach MC, Sparrey J, Gonzalez-Sulser A, Martin JE
Publication type: Article
Publication status: Published
Journal: Lab Animal
Year: 2026
Issue: ePub ahead of print
Online publication date: 21/08/2026
Acceptance date: 21/07/2026
Date deposited: 22/07/2026
ISSN (print): 0093-7355
ISSN (electronic): 1548-4475
Publisher: Springer
URL: https://doi.org/10.1038/s41684-026-01788-5
DOI: 10.1038/s41684-026-01788-5
ePrints DOI: 10.57711/sv10-z720
Data Access Statement: Data supporting this study are openly available in Zenodo at 10.5281/zenodo.21220901.
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