Body surface temperature of rats reveals both magnitude and sex differences in the acute stress response

Wongsaengchan, C., McCafferty, D. J. , Evans, N. P. , McKeegan, D. E.F. and Nager, R. G. (2023) Body surface temperature of rats reveals both magnitude and sex differences in the acute stress response. Physiology and Behavior, 264, 114138. (doi: 10.1016/j.physbeh.2023.114138) (PMID:36871696)

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Understanding how biological markers of stress relate to stressor magnitude is much needed and can be used in welfare assessment. Changes in body surface temperature can be measured using infrared thermography (IRT) as a marker of a physiological response to acute stress. While an avian study has shown that changes in body surface temperature can reflect the intensity of acute stress, little is known about surface temperature responses to stressors of different magnitudes and its sex-specificity in mammals, and how they correlate with hormonal and behavioural responses. We used IRT to collect continuous surface temperature measurements of tail and eye of adult male and female rats (Rattus norvegicus), for 30 minutes after exposure to one of three stressors (small cage, encircling handling or rodent restraint cone) for one minute, and cross-validated the thermal response with plasma corticosterone (CORT) and behavioural assessment. To obtain individual baseline temperatures and thermal responses to stress, rats were imaged in a test arena (to which they were habituated) for 30 seconds before and 30 minutes after being exposed to the stressor. In response to the three stressors, tail temperature initially decreased and then recovered to, or overshot the baseline temperature. Tail temperature dynamics differed between stressors; being restrained in the small cage was associated with the smallest drop in temperature, in male rats, and the fastest thermal recovery, in both sexes. Increases in eye temperature only distinguished between stressors early in the response and only in females. The post stressor increase in eye temperature was greater in the right eye of males and the left eye of females. In both sexes encircling may have been associated with the fastest increase in CORT. These results were in line with observed behavioural changes, with greater movement in rats exposed to the small cage and higher immobility after encircling. The female tail and eye temperature, as well as the CORT concentrations did not return to pre-stressor levels in the observation period, in conjunction with the greater occurrence of escape-related behaviours in female rats. These results suggest that female rats are more vulnerable to acute restraint stress compared to male rats and emphasise the importance of using both sexes in future investigations of stressor magnitude. This study demonstrates that acute stress induced changes in mammalian surface temperature measured with IRT relate to the magnitude of restraint stress, indicate sex differences and correlate with hormonal and behavioural responses. Thus, IRT has the potential to become a non-invasive method of continuous welfare assessment in unrestrained mammals.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Wongsaengchan, Chanakarn and McKeegan, Dr Dorothy and Nager, Dr Ruedi and McCafferty, Dr Dominic and Evans, Professor Neil
Authors: Wongsaengchan, C., McCafferty, D. J., Evans, N. P., McKeegan, D. E.F., and Nager, R. G.
Subjects:Q Science > QH Natural history > QH301 Biology
Q Science > QL Zoology
Q Science > QP Physiology
College/School:College of Medical Veterinary and Life Sciences > School of Biodiversity, One Health & Veterinary Medicine
Journal Name:Physiology and Behavior
ISSN (Online):1873-507X
Published Online:05 March 2023
Copyright Holders:Copyright © 2023 The Authors
First Published:First published in Physiology and Behavior 264: 114138
Publisher Policy:Reproduced under a Creative Commons License
Data DOI:10.17632/8k5z5bx2s8.1

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
190530Thermography as a tool for the assessment of stress and affective states in an avian modelDorothy McKeeganBiotechnology and Biological Sciences Research Council (BBSRC)BB/K002775/1Institute of Biodiversity, Animal Health and Comparative Medicine