Relationship between behaviour and tail temperature of tickled and gentled rats before, during and after manual restraint stress
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Many routine procedures in experiments, such as handling, cause stress in rats. Rat tickling is a technique which aims to reduce handling stress. In a previous study, the effect of tickling or gentling on tail temperatures of rats was investigated, using infrared thermography. The present study analyses the behaviour of the rats from the mentioned study, to investigate possible effects of stress-related and other behaviours on tail temperature. Moreover, the effect of two different handling techniques, tickling and gentling, on behaviour was analysed. Sixteen male Wistar rats (WU:Crl) received one of the following treatments for 14 weeks: tickling (n = 8), gentling (n = 4) or no handling (control, n = 4). Mid-tail temperature was measured before, during and after manual restraint, and videos for behavioural analysis were recorded. Results showed that higher groom, scratch and rear frequencies are associated with higher tail temperatures, while no effect of freezing or huddling on tail temperature was found. Moreover, gentled rats froze less than control rats and tickled rats during the stressor, and less than control rats post-stressor. Gentled rats also huddled the most pre-stressor. Control rats spent the most time grooming pre-stressor, while they had the highest groom frequency post-stressor. Post-stressor, the average groom bout duration was longer for Tickled rats than for Gentled rats. The results of freeze durations suggest that tickling did not reduce fear in response to manual restraint, at least not in all rats. Tickling might not always be a positive experience for rats. This study is limited by its sample size, with possible cage effects influencing the results. Additional research is suggested.