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Avoidance and contextual learning induced by a kairomone, a pheromone and a common odorant in female CD1 mice.

Fortes-Marco L, Lanuza E, Martínez-García F, Agustín-Pavón C - Front Neurosci (2015)

Bottom Line: All three compounds induced minimal effects in global locomotion and immobility in this set up.Our results support that synthetic predator-related compounds (like TMT) or other intense odorants are useful to investigate the neurobiological basis of emotional behaviors in rodents.Since intense odorants unlikely to act as chemosignals can elicit similar behavioral reactions than chemosignals, we stress the importance of using behavioral measures in combination with other physiological (e.g., hormonal levels) or neural measures (e.g., immediate early gene expression) to establish the ethological significance of odorants.

View Article: PubMed Central - PubMed

Affiliation: Unitat Pre-departamental de Medicina, Facultad de Ciencias de la Salud, Universitat Jaume I Castelló de la Plana, Spain ; Departament de Biologia Cel·lular, Facultat de Ciències Biològiques, Universitat de València València, Spain.

ABSTRACT
Chemosignals mediate both intra- and inter-specific communication in most mammals. Pheromones elicit stereotyped reactions in conspecifics, whereas kairomones provoke a reaction in an allospecific animal. For instance, predator kairomones elicit anticipated defensive responses in preys. The aim of this work was to test the behavioral responses of female mice to two chemosignals: 2-heptanone (2-HP), a putative alarm pheromone, and 2,4,5-trimethylthiazoline (TMT), a fox-derived putative kairomone, widely used to investigate fear and anxiety in rodents. The banana-like odorant isoamyl acetate (IA), unlikely to act as a chemosignal, served as a control odorant. We first presented increasing amounts of these odorants in consecutive days, in a test box in which mice could explore or avoid them. Female mice avoided the highest amounts of all three compounds, with TMT and IA eliciting avoidance at lower amounts (3.8 pmol and 0.35 μmol, respectively) than 2-HP (35 μmol). All three compounds induced minimal effects in global locomotion and immobility in this set up. Further, mice detected 3.5 pmol of TMT and IA in a habituation-dishabituation test, so avoidance of IA started well beyond the detection threshold. Finally, both TMT and IA, but not 2-HP, induced conditioned place avoidance and increased immobility in the neutral compartment during a contextual memory test. These data suggest that intense odors can induce contextual learning irrespective of their putative biological significance. Our results support that synthetic predator-related compounds (like TMT) or other intense odorants are useful to investigate the neurobiological basis of emotional behaviors in rodents. Since intense odorants unlikely to act as chemosignals can elicit similar behavioral reactions than chemosignals, we stress the importance of using behavioral measures in combination with other physiological (e.g., hormonal levels) or neural measures (e.g., immediate early gene expression) to establish the ethological significance of odorants.

No MeSH data available.


Related in: MedlinePlus

TMT and IA, but not 2-HP, induced contextual learning. Bar charts representing behavioral responses in the contextual learning experiment, in the pre-exposure control (Control) and the contextual memory test (Test). Mice exposed to pure TMT during four consecutive sessions expressed conditioned place avoidance to the zone paired with the stimulus, as shown by a significant decrease of the avoidance ratio in the test (A). In addition, TMT failed to affect distance traveled (B), but increased immobility in the neutral zone during the test (C), suggesting that animals avoided TMT and stayed immobile in the neutral zone. By contrast, 2-HP did not induce a contextual memory, since it did not affect the avoidance ratio (D), but, overall, it slightly decreased distance traveled (E), and did not affect immobility (F). Finally, IA produced a marginally significant decrease in the avoidance ratio (G), and significantly decreased distance traveled (H). Like TMT, IA increased immobility in the neutral zone (I). *p < 0.05. Comparison between the neutral zones in control and test: a, p < 0.05. Data are expressed as mean ± SEM.
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Figure 3: TMT and IA, but not 2-HP, induced contextual learning. Bar charts representing behavioral responses in the contextual learning experiment, in the pre-exposure control (Control) and the contextual memory test (Test). Mice exposed to pure TMT during four consecutive sessions expressed conditioned place avoidance to the zone paired with the stimulus, as shown by a significant decrease of the avoidance ratio in the test (A). In addition, TMT failed to affect distance traveled (B), but increased immobility in the neutral zone during the test (C), suggesting that animals avoided TMT and stayed immobile in the neutral zone. By contrast, 2-HP did not induce a contextual memory, since it did not affect the avoidance ratio (D), but, overall, it slightly decreased distance traveled (E), and did not affect immobility (F). Finally, IA produced a marginally significant decrease in the avoidance ratio (G), and significantly decreased distance traveled (H). Like TMT, IA increased immobility in the neutral zone (I). *p < 0.05. Comparison between the neutral zones in control and test: a, p < 0.05. Data are expressed as mean ± SEM.

Mentions: Mice of the TMT group expressed a conditioned avoidance for the stimulus chamber after four consecutive days of exposure to this kairomone (Student's t-test of the avoidance ratio control vs. place conditioning test, p = 0.029; Figure 3A). Moreover, a Student's t-test against the chance value 0.5 revealed that the avoidance ratio was significantly different from chance in the test (p = 0.027) but not the pre-training control (p = 0.64). However, neither distance traveled nor global percentage of immobility were significantly different between the control and the place conditioning test (p = 0.7, Figure 3B). We further explored whether the percentage of immobility would be dependent on the zone, i.e., whether mice would stay inactive in the neutral or the stimulus zone (Fortes-Marco et al., 2013). Indeed, there was a significant difference between zones in the place conditioning test, driven by an increase in the percentage of immobility in the neutral zone in the test with respect to control [repeated measures ANOVA, DAY × ZONE, F(1, 10) = 8.7, p = 0.014, post-hoc stimulus vs. neutral zone in the test, p = 0.002; post-hoc time spent in neutral zone in control vs. test, p = 0.017; Figure 3C].


Avoidance and contextual learning induced by a kairomone, a pheromone and a common odorant in female CD1 mice.

Fortes-Marco L, Lanuza E, Martínez-García F, Agustín-Pavón C - Front Neurosci (2015)

TMT and IA, but not 2-HP, induced contextual learning. Bar charts representing behavioral responses in the contextual learning experiment, in the pre-exposure control (Control) and the contextual memory test (Test). Mice exposed to pure TMT during four consecutive sessions expressed conditioned place avoidance to the zone paired with the stimulus, as shown by a significant decrease of the avoidance ratio in the test (A). In addition, TMT failed to affect distance traveled (B), but increased immobility in the neutral zone during the test (C), suggesting that animals avoided TMT and stayed immobile in the neutral zone. By contrast, 2-HP did not induce a contextual memory, since it did not affect the avoidance ratio (D), but, overall, it slightly decreased distance traveled (E), and did not affect immobility (F). Finally, IA produced a marginally significant decrease in the avoidance ratio (G), and significantly decreased distance traveled (H). Like TMT, IA increased immobility in the neutral zone (I). *p < 0.05. Comparison between the neutral zones in control and test: a, p < 0.05. Data are expressed as mean ± SEM.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4594011&req=5

Figure 3: TMT and IA, but not 2-HP, induced contextual learning. Bar charts representing behavioral responses in the contextual learning experiment, in the pre-exposure control (Control) and the contextual memory test (Test). Mice exposed to pure TMT during four consecutive sessions expressed conditioned place avoidance to the zone paired with the stimulus, as shown by a significant decrease of the avoidance ratio in the test (A). In addition, TMT failed to affect distance traveled (B), but increased immobility in the neutral zone during the test (C), suggesting that animals avoided TMT and stayed immobile in the neutral zone. By contrast, 2-HP did not induce a contextual memory, since it did not affect the avoidance ratio (D), but, overall, it slightly decreased distance traveled (E), and did not affect immobility (F). Finally, IA produced a marginally significant decrease in the avoidance ratio (G), and significantly decreased distance traveled (H). Like TMT, IA increased immobility in the neutral zone (I). *p < 0.05. Comparison between the neutral zones in control and test: a, p < 0.05. Data are expressed as mean ± SEM.
Mentions: Mice of the TMT group expressed a conditioned avoidance for the stimulus chamber after four consecutive days of exposure to this kairomone (Student's t-test of the avoidance ratio control vs. place conditioning test, p = 0.029; Figure 3A). Moreover, a Student's t-test against the chance value 0.5 revealed that the avoidance ratio was significantly different from chance in the test (p = 0.027) but not the pre-training control (p = 0.64). However, neither distance traveled nor global percentage of immobility were significantly different between the control and the place conditioning test (p = 0.7, Figure 3B). We further explored whether the percentage of immobility would be dependent on the zone, i.e., whether mice would stay inactive in the neutral or the stimulus zone (Fortes-Marco et al., 2013). Indeed, there was a significant difference between zones in the place conditioning test, driven by an increase in the percentage of immobility in the neutral zone in the test with respect to control [repeated measures ANOVA, DAY × ZONE, F(1, 10) = 8.7, p = 0.014, post-hoc stimulus vs. neutral zone in the test, p = 0.002; post-hoc time spent in neutral zone in control vs. test, p = 0.017; Figure 3C].

Bottom Line: All three compounds induced minimal effects in global locomotion and immobility in this set up.Our results support that synthetic predator-related compounds (like TMT) or other intense odorants are useful to investigate the neurobiological basis of emotional behaviors in rodents.Since intense odorants unlikely to act as chemosignals can elicit similar behavioral reactions than chemosignals, we stress the importance of using behavioral measures in combination with other physiological (e.g., hormonal levels) or neural measures (e.g., immediate early gene expression) to establish the ethological significance of odorants.

View Article: PubMed Central - PubMed

Affiliation: Unitat Pre-departamental de Medicina, Facultad de Ciencias de la Salud, Universitat Jaume I Castelló de la Plana, Spain ; Departament de Biologia Cel·lular, Facultat de Ciències Biològiques, Universitat de València València, Spain.

ABSTRACT
Chemosignals mediate both intra- and inter-specific communication in most mammals. Pheromones elicit stereotyped reactions in conspecifics, whereas kairomones provoke a reaction in an allospecific animal. For instance, predator kairomones elicit anticipated defensive responses in preys. The aim of this work was to test the behavioral responses of female mice to two chemosignals: 2-heptanone (2-HP), a putative alarm pheromone, and 2,4,5-trimethylthiazoline (TMT), a fox-derived putative kairomone, widely used to investigate fear and anxiety in rodents. The banana-like odorant isoamyl acetate (IA), unlikely to act as a chemosignal, served as a control odorant. We first presented increasing amounts of these odorants in consecutive days, in a test box in which mice could explore or avoid them. Female mice avoided the highest amounts of all three compounds, with TMT and IA eliciting avoidance at lower amounts (3.8 pmol and 0.35 μmol, respectively) than 2-HP (35 μmol). All three compounds induced minimal effects in global locomotion and immobility in this set up. Further, mice detected 3.5 pmol of TMT and IA in a habituation-dishabituation test, so avoidance of IA started well beyond the detection threshold. Finally, both TMT and IA, but not 2-HP, induced conditioned place avoidance and increased immobility in the neutral compartment during a contextual memory test. These data suggest that intense odors can induce contextual learning irrespective of their putative biological significance. Our results support that synthetic predator-related compounds (like TMT) or other intense odorants are useful to investigate the neurobiological basis of emotional behaviors in rodents. Since intense odorants unlikely to act as chemosignals can elicit similar behavioral reactions than chemosignals, we stress the importance of using behavioral measures in combination with other physiological (e.g., hormonal levels) or neural measures (e.g., immediate early gene expression) to establish the ethological significance of odorants.

No MeSH data available.


Related in: MedlinePlus