Positive emotion-specific changes in the gene expression profile of tickled rats

Hori, Manabu; Hayashi, Takashi; Nakagawa, Yoshimi; Sakamoto, Sadao; Urayama, Osamu; Murakami, Kazuo

doi:10.3892/mmr_00000077

Cited by 4 publications

(6 citation statements)

References 19 publications

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“…Common findings include increased production of 50-kHz USVs, increased approach behavior, and increased ease of handling. Reported effects of rat tickling at the genetic and cellular level include altered gene expression in the hypothalamus 37 , and increased neurogenesis in the dentate gyrus of the hippocampus 38 39 . Outcomes indicative of reduced generalized anxiety and fear of humans are also reported such as reduced latency to approach in 9 different experiments 13 , less freezing after fear conditioning 40 41 , and increased entries into the center of an open field arena by individually housed rats 36 .…”

Section: Representative Resultsmentioning

confidence: 99%

Tickling, a Technique for Inducing Positive Affect When Handling Rats

Cloutier

LaFollette

Gaskill

et al. 2018

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Handling small animals such as rats can lead to several adverse effects. These include the fear of humans, resistance to handling, increased injury risk for both the animals and the hands of their handlers, decreased animal welfare, and less valid research data. To minimize negative effects on experimental results and human-animal relationships, research animals are often habituated to being handled. However, the methods of habituation are highly variable and often of limited effectiveness. More potently, it is possible for humans to mimic aspects of the animals' playful rough-and-tumble behavior during handling. When applied to laboratory rats in a systematic manner, this playful handling, referred to as tickling, consistently gives rise to positive behavioral responses. This article provides a detailed description of a standardized rat tickling technique. This method can contribute to future investigations into positive affective states in animals, make it easier to handle rats for common husbandry activities such as cage changing or medical/research procedures such as injection, and be implemented as a source of social enrichment. It is concluded that this method can be used to efficiently and practicably reduce rats' fearfulness of humans and improve their welfare, as well as reliably model positive affective states.

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Section: Representative Resultsmentioning

confidence: 99%

Tickling, a Technique for Inducing Positive Affect When Handling Rats

Cloutier

LaFollette

Gaskill

et al. 2018

JoVE

View full text Add to dashboard Cite

show abstract

“…The two experiments that found an effect of handling treatment used a light touch comparison condition [21, 22]. The three experiments that found no effect of tickling treatment used a minimal handling, restraint, or passive hand comparison condition [4, 23, 24].…”

Section: Resultsmentioning

confidence: 99%

“…Adult hippocampus cell proliferation is a factor associated with depression. Tickling altered the expression of genes in the hypothalamus related to feeding regulation [21]. This experiment was an attempt to model and investigate the effect seen in humans that blood glucose levels improve after laughter.…”

Section: Resultsmentioning

confidence: 99%

“…This experiment was an attempt to model and investigate the effect seen in humans that blood glucose levels improve after laughter. [21]. Tickling increased neurogenesis in the dentate gyrus of the hippocampus [29].…”

Section: Resultsmentioning

confidence: 99%

“…To investigate this trait vs state controversy, one experiment used tickling and individual differences in calling rate to show that hippocampal cell proliferation depends on an interaction between a pre-disposing trait and stimulation-depending variations in the subject’s affective state [19]. Additionally, a series of studies used tickling to model laughter in humans and study its effects on gene expression and neurogenesis in the brain and salivary glands [21, 29, 30]. Tickling is useful for studying positive affect because it can be used quickly, consistently and reliably in contrast to other tests such as cognitive bias or sucrose consumption.…”

Section: Discussionmentioning

confidence: 99%

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Rat tickling: A systematic review of applications, outcomes, and moderators

et al. 2017

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IntroductionRats initially fear humans which can increase stress and impact study results. Additionally, studying positive affective states in rats has proved challenging. Rat tickling is a promising habituation technique that can also be used to model and measure positive affect. However, current studies use a variety of methods to achieve differential results. Our objective was to systematically identify, summarize, and evaluate the research on tickling in rats to provide direction for future investigation. Our specific aims were to summarize current methods used in tickling experiments, outcomes from tickling, and moderating factors.MethodsWe systematically evaluated all articles about tickling identified from PubMed, Scopus, Web of Science, and PsychInfo. Our inclusion criteria were publication in a peer-reviewed journal and collection of original, empirical data on rats using the handling method of tickling. One researcher extracted information from each article. Bias was assessed by 2 investigators using the SYRCLE bias assessment tool.ResultsWe identified 32 articles (56 experiments) published in peer-reviewed journals about rat tickling for inclusion. A wide variety of strains, sexes, and ages of rats were included. The most common method used for tickling was cycling through 15 seconds of tickling and 15 seconds of rest for 2 minutes for 3 to 5 days. Experiments with a control for tickling (N = 22) showed that tickling increases positive vocalization, approach behavior, decreases anxiety measures, improves handling, and in some cases decreases stress hormones. Tickling juvenile, individually housed rats with a trait predisposition to respond more positively to tickling, results in the most positive outcomes. Methods to reduce bias were insufficiently reported.ConclusionsWe conclude that tickling is a promising method for improving rat welfare and investigating positive affect. However, the establishment of tickling best practices is essential as the outcomes from tickling can be moderated by several factors.

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Stroking stimulation of the skin elicits 50-kHz ultrasonic vocalizations in young adult rats

et al. 2020

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The present study aimed to clarify if stroking stimulation of the skin produces positive emotion in rats. 50-kHz ultrasonic vocalizations (USVs) were recorded as an index of the positive emotion. Stroking stimulation was applied to the ventral, dorsal, or head region of the body while the rat was in a vertical holding condition. Rats emit abundant 50-kHz USVs in response to stroking, and the number of the USVs was not different among these three stimulated regions. Other stimulations, such as light touching of the abdominal area, swinging of the body back and forth, or stroking of the external genitalia under vertical holding condition, produced significantly less 50-kHz USVs. Furthermore, different call subtypes were observed during and after stroking of the ventral region. In particular, “Trill” calls, a representative index of positive emotion, were dominant after stimulation. These results suggest that stroking of the skin induces positive emotional states.

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Positive emotion-specific changes in the gene expression profile of tickled rats

Cited by 4 publications

References 19 publications

Tickling, a Technique for Inducing Positive Affect When Handling Rats

Tickling, a Technique for Inducing Positive Affect When Handling Rats

Rat tickling: A systematic review of applications, outcomes, and moderators

Stroking stimulation of the skin elicits 50-kHz ultrasonic vocalizations in young adult rats

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