Dataset Information

Odour conditioning of positive affective states: Rats can learn to associate an odour with being tickled.

ABSTRACT: Most associative learning tests in rodents use negative stimuli, such as electric shocks. We investigated if young rats can learn to associate the presence of an odour with the experience of being tickled (i.e. using an experimenter's hand to mimic rough-and-tumble play), shown to elicit 50 kHz ultrasonic vocalisations (USVs), which are indicative of positive affect. Male, pair-housed Wistar rats (N = 24) were all exposed to two neutral odours (A and B) presented in a perforated container on alternate days in a test arena. Following 60s of exposure, the rats were either tickled on days when odour A (n = 8) or odour B (n = 8) was present, or never tickled (n = 8). When tickled, rats produced significantly more 50 kHz USVs compared to the days when not being tickled, and compared to control rats. The level of anticipatory 50 kHz USVs in the 60s prior to tickling did not differ significantly between the tickled and control rats. As a retrieval test following the odour conditioning, rats were exposed successively in the same arena to three odours: an unknown neutral odour, extract of fox faeces, and either odours A or B. Compared to controls, 50 kHz USVs of tickled rats increased when exposed to the odour they had previously experienced when tickled, indicating that these rats had learned to associate the odour with the positive experience of being tickled. In a test with free access for 5 min to both arms of a T-maze, each containing one of the odours, rats tickled with odour A spent more time in the arm with this odour. This work is the first to test in a fully balanced design whether rats can learn to associate an odour with tickling, and indicates that positive odour conditioning has potential to be used as an alternative to negative conditioning tests.

SUBMITTER: Bombail V

PROVIDER: S-EPMC6561538 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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Odour conditioning of positive affective states: Rats can learn to associate an odour with being tickled.

Bombail Vincent V Jerôme Nathalie N Lam Ho H Muszlak Sacha S Meddle Simone L SL Lawrence Alistair B AB Nielsen Birte L BL

PloS one 20190612 6

Most associative learning tests in rodents use negative stimuli, such as electric shocks. We investigated if young rats can learn to associate the presence of an odour with the experience of being tickled (i.e. using an experimenter's hand to mimic rough-and-tumble play), shown to elicit 50 kHz ultrasonic vocalisations (USVs), which are indicative of positive affect. Male, pair-housed Wistar rats (N = 24) were all exposed to two neutral odours (A and B) presented in a perforated container on alt ...[more]

PMID: 31188832

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Project description:BackgroundReliable recognition of individuals requires phenotypic identity signatures that are both individually distinctive and appropriately stable over time. Individual-specific vocalisations or visual patterning are well documented among birds and some mammals, whilst odours play a key role in social recognition across many vertebrates and invertebrates. Less well understood, though, is whether individuals are recognised through variation in cues that arise incidentally from a wide variety of genetic and non-genetic differences between individuals, or whether animals evolve distinctive polymorphic signals to advertise identity reliably. As a bioassay to understand the derivation of individual-specific odour signatures, we use female attraction to the individual odours of male house mice (Mus musculus domesticus), learned on contact with a male's scent marks.ResultsLearned volatile odour signatures are determined predominantly by individual differences in involatile major urinary protein (MUP) signatures, a specialised set of communication proteins that mice secrete in their urine. Recognition of odour signatures in genetically distinct mice depended on differences in individual MUP genotype. Direct manipulation using recombinant MUPs confirmed predictable changes in volatile signature recognition according to the degree of matching between MUP profiles and the learned urine template. Both the relative amount of the male-specific MUP pheromone darcin, which induces odour learning, and other MUP isoforms influenced learned odour signatures. By contrast, odour recognition was not significantly influenced by individual major histocompatibility complex genotype. MUP profiles shape volatile odour signatures through isoform-specific differences in binding and release of urinary volatiles from scent deposits, such that volatile signatures were recognised from the urinary protein fraction alone. Manipulation using recombinant MUPs led to quantitative changes in the release of known MUP ligands from scent deposits, with MUP-specific and volatile-specific effects.ConclusionsDespite assumptions that many genes contribute to odours that can be used to recognise individuals, mice have evolved a polymorphic combinatorial MUP signature that shapes distinctive volatile signatures in their scent. Such specific signals may be more prevalent within complex body odours than previously realised, contributing to the evolution of phenotypic diversity within species. However, differences in selection may also result in species-specific constraints on the ability to recognise individuals through complex body scents.

Project description:Ultrasonic vocalizations in the 50 kHz range (50 kHz USVs) are emitted by rodents upon activation of positive affective states and appear to be a direct measure of internal emotional and motivational urges to seek rewarding stimuli such as drugs of abuse. Since these behavioral responses do not rely on training for expression, they can be viewed as a "spontaneous" measure of affective state. The goal of the present study was to monitor spontaneous USVs throughout a widely-used cocaine self-administration and reinstatement model of addiction and relapse. To gain insight into the changes in affective state across the different phases of a standard self-administration experiment, we measured 50 kHz USVs in rats during cocaine self-administration and reinstatement, and compared these to sucrose self-administration and reinstatement. During cocaine self-administration, the number of 50 kHz USVs increased over acquisition of self-administration and decreased during extinction. Furthermore, the number of USVs on the first day of acquisition in the cocaine experiment was positively correlated with how rapidly cocaine self-administration was acquired. These findings suggest that the initial affective response to cocaine may be a sensitive predictor of the motivational efficacy of rewarding stimuli and therefore the susceptibility to acquire self-administration of cocaine. Cue- and cocaine-induced reinstatement elevated 50 kHz USVs above extinction levels. Rats trained for sucrose self-administration showed no elevation in USVs during acquisition when USVs were considered over the entire 2 h session, but they did show an elevation in USVs during acquisition when considered over only the first 5 min of the session. As with cocaine-induced reinstatement, sucrose-induced reinstatement produced significantly more USVs compared to the prior extinction day. Taken together, USVs may serve as a sensitive and dynamic non-invasive measure that spontaneously (i.e. without any formal reinforcement contingencies) quantifies the extent to which positive affect is elicited by rewards such as drugs of abuse.

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Odour conditioning of positive affective states: Rats can learn to associate an odour with being tickled.

Publications

Odour conditioning of positive affective states: Rats can learn to associate an odour with being tickled.

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