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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

Pure TMT, 2-HP and IA were avoided and differently affected locomotion. Line charts representing behavioral responses during the training days of the contextual conditioning experiment for each odorant. All three odors were significantly avoided, but the avoidance of TMT was blunted across sessions, whereas avoidance of 2-HP increased in the second day (A). Distance traveled was differentially affected by the three odors: whereas TMT increased locomotion during the first exposure day and then this parameter remained stable, 2-HP and IA decreased locomotion across tests (B). TMT reduced immobility the first training day, and 2-HP increased it during the last training day, whereas IA did not affect to this measure (C). Comparison between odorants: *p < 0.05. Comparison between exposure days and the control situation: a, p < 0.05. Data are expressed as mean ± SEM.
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Figure 4: Pure TMT, 2-HP and IA were avoided and differently affected locomotion. Line charts representing behavioral responses during the training days of the contextual conditioning experiment for each odorant. All three odors were significantly avoided, but the avoidance of TMT was blunted across sessions, whereas avoidance of 2-HP increased in the second day (A). Distance traveled was differentially affected by the three odors: whereas TMT increased locomotion during the first exposure day and then this parameter remained stable, 2-HP and IA decreased locomotion across tests (B). TMT reduced immobility the first training day, and 2-HP increased it during the last training day, whereas IA did not affect to this measure (C). Comparison between odorants: *p < 0.05. Comparison between exposure days and the control situation: a, p < 0.05. Data are expressed as mean ± SEM.

Mentions: To check whether the different effects of each odorant in memory and activity were due to differential effects of the repeated exposure to them, we compared the avoidance ratio, distance traveled and immobility during the training days between groups (TMT, 2-HP and IA). The avoidance ratio of the groups exposed to TMT and 2-HP was significantly different to those of IA [repeated measures ANOVA, DAY × ODOR, F(6, 96) = 3.1, p = 0.01; post-hoc comparison TMT vs. IA and 2-HP and 2-HP vs. IA, both p = 0.023; Figure 4A]. Further post-hoc pairwise comparisons between the individual exposure days revealed that all odors were equally avoided during the first two training days, but from day 3, the avoidance ratio of TMT decreased and became significantly different from both 2-HP and IA (p < 0.05 in all cases; Figure 4A). In fact, the avoidance ratio in the TMT group was significantly different between day 2 and 3 (p = 0.042). Conversely, the avoidance ratio of the group exposed to 2-HP was significantly lower in day 2 than in day 1 (p = 0.02). Finally, the avoidance ratio of the group exposed to IA did not vary across days. These findings suggest that mice were slightly habituated to the aversive properties of TMT, whereas they expressed a higher avoidance of 2-HP in consecutive tests.


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)

Pure TMT, 2-HP and IA were avoided and differently affected locomotion. Line charts representing behavioral responses during the training days of the contextual conditioning experiment for each odorant. All three odors were significantly avoided, but the avoidance of TMT was blunted across sessions, whereas avoidance of 2-HP increased in the second day (A). Distance traveled was differentially affected by the three odors: whereas TMT increased locomotion during the first exposure day and then this parameter remained stable, 2-HP and IA decreased locomotion across tests (B). TMT reduced immobility the first training day, and 2-HP increased it during the last training day, whereas IA did not affect to this measure (C). Comparison between odorants: *p < 0.05. Comparison between exposure days and the control situation: a, p < 0.05. Data are expressed as mean ± SEM.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 4: Pure TMT, 2-HP and IA were avoided and differently affected locomotion. Line charts representing behavioral responses during the training days of the contextual conditioning experiment for each odorant. All three odors were significantly avoided, but the avoidance of TMT was blunted across sessions, whereas avoidance of 2-HP increased in the second day (A). Distance traveled was differentially affected by the three odors: whereas TMT increased locomotion during the first exposure day and then this parameter remained stable, 2-HP and IA decreased locomotion across tests (B). TMT reduced immobility the first training day, and 2-HP increased it during the last training day, whereas IA did not affect to this measure (C). Comparison between odorants: *p < 0.05. Comparison between exposure days and the control situation: a, p < 0.05. Data are expressed as mean ± SEM.
Mentions: To check whether the different effects of each odorant in memory and activity were due to differential effects of the repeated exposure to them, we compared the avoidance ratio, distance traveled and immobility during the training days between groups (TMT, 2-HP and IA). The avoidance ratio of the groups exposed to TMT and 2-HP was significantly different to those of IA [repeated measures ANOVA, DAY × ODOR, F(6, 96) = 3.1, p = 0.01; post-hoc comparison TMT vs. IA and 2-HP and 2-HP vs. IA, both p = 0.023; Figure 4A]. Further post-hoc pairwise comparisons between the individual exposure days revealed that all odors were equally avoided during the first two training days, but from day 3, the avoidance ratio of TMT decreased and became significantly different from both 2-HP and IA (p < 0.05 in all cases; Figure 4A). In fact, the avoidance ratio in the TMT group was significantly different between day 2 and 3 (p = 0.042). Conversely, the avoidance ratio of the group exposed to 2-HP was significantly lower in day 2 than in day 1 (p = 0.02). Finally, the avoidance ratio of the group exposed to IA did not vary across days. These findings suggest that mice were slightly habituated to the aversive properties of TMT, whereas they expressed a higher avoidance of 2-HP in consecutive tests.

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