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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, 2-HP, and IA induced avoidance in a concentration-dependent way. Bar and line charts representing the avoidance ratio and time spent in each zone for increasing concentrations of each odorant. For all three odorants, the avoidance ratio was significantly different from the control situation (no odor) only when pure substance was presented (A,C,E, *p < 0.05). Time spent by the animals at the stimulus zone was dose-dependently decreased by TMT with respect to the neutral zone (B), whereas 2-HP did not induce avoidance except when presented pure (D). Finally, IA produced a pattern of avoidance similar to that of TMT (F). Comparison between the stimulus zone with the same zone in the control (no odor): a, p < 0.05. Comparison between the stimulus and the neutral zones: b, p < 0.05. Data are represented as mean ± SEM.
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Figure 1: TMT, 2-HP, and IA induced avoidance in a concentration-dependent way. Bar and line charts representing the avoidance ratio and time spent in each zone for increasing concentrations of each odorant. For all three odorants, the avoidance ratio was significantly different from the control situation (no odor) only when pure substance was presented (A,C,E, *p < 0.05). Time spent by the animals at the stimulus zone was dose-dependently decreased by TMT with respect to the neutral zone (B), whereas 2-HP did not induce avoidance except when presented pure (D). Finally, IA produced a pattern of avoidance similar to that of TMT (F). Comparison between the stimulus zone with the same zone in the control (no odor): a, p < 0.05. Comparison between the stimulus and the neutral zones: b, p < 0.05. Data are represented as mean ± SEM.

Mentions: The avoidance ratio for the group exposed to TMT was significantly different from control at the highest amount of TMT used [repeated measures ANOVA, factor CONCENTRATION, F(9, 99) = 4.9, p < 0.001; post-hoc comparison between exposure day 9 (38 μmol of TMT) vs. control (no TMT), p = 0.009; Figure 1A]. We further checked whether there was a difference in the raw time that animals spent in each zone. There was a significant decrease of the time spent in the stimulus zone when it contained 38 μmol of TMT with respect to the stimulus zone in the control day [repeated measures ANOVA, CONCENTRATION × ZONE, F(9, 99) = 3.6, p < 0.001; post-hoc comparison for exposure day 9, stimulus zone vs. control, p = 0.001; Figure 1B]. Still, post-hoc pairwise comparisons between zones showed that time spent in the TMT zone was lower with respect to the neutral zone during exposure days 2, 4, 8, and 9 (3.8 pmol, p = 0.023; 0.38 nmol, p = 0.015; 3.8 μmol, p = 0.002; and 38 μmol, p < 0.001; Figure 1B). These results suggest that mice were able to detect TMT from 3.8 pmol, since this amount induced a slight avoidance reaction (Figure 1B), but TMT was strongly avoided at pure concentration only as measured with both time spent in zones and avoidance ratio.


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, 2-HP, and IA induced avoidance in a concentration-dependent way. Bar and line charts representing the avoidance ratio and time spent in each zone for increasing concentrations of each odorant. For all three odorants, the avoidance ratio was significantly different from the control situation (no odor) only when pure substance was presented (A,C,E, *p < 0.05). Time spent by the animals at the stimulus zone was dose-dependently decreased by TMT with respect to the neutral zone (B), whereas 2-HP did not induce avoidance except when presented pure (D). Finally, IA produced a pattern of avoidance similar to that of TMT (F). Comparison between the stimulus zone with the same zone in the control (no odor): a, p < 0.05. Comparison between the stimulus and the neutral zones: b, p < 0.05. Data are represented as mean ± SEM.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 1: TMT, 2-HP, and IA induced avoidance in a concentration-dependent way. Bar and line charts representing the avoidance ratio and time spent in each zone for increasing concentrations of each odorant. For all three odorants, the avoidance ratio was significantly different from the control situation (no odor) only when pure substance was presented (A,C,E, *p < 0.05). Time spent by the animals at the stimulus zone was dose-dependently decreased by TMT with respect to the neutral zone (B), whereas 2-HP did not induce avoidance except when presented pure (D). Finally, IA produced a pattern of avoidance similar to that of TMT (F). Comparison between the stimulus zone with the same zone in the control (no odor): a, p < 0.05. Comparison between the stimulus and the neutral zones: b, p < 0.05. Data are represented as mean ± SEM.
Mentions: The avoidance ratio for the group exposed to TMT was significantly different from control at the highest amount of TMT used [repeated measures ANOVA, factor CONCENTRATION, F(9, 99) = 4.9, p < 0.001; post-hoc comparison between exposure day 9 (38 μmol of TMT) vs. control (no TMT), p = 0.009; Figure 1A]. We further checked whether there was a difference in the raw time that animals spent in each zone. There was a significant decrease of the time spent in the stimulus zone when it contained 38 μmol of TMT with respect to the stimulus zone in the control day [repeated measures ANOVA, CONCENTRATION × ZONE, F(9, 99) = 3.6, p < 0.001; post-hoc comparison for exposure day 9, stimulus zone vs. control, p = 0.001; Figure 1B]. Still, post-hoc pairwise comparisons between zones showed that time spent in the TMT zone was lower with respect to the neutral zone during exposure days 2, 4, 8, and 9 (3.8 pmol, p = 0.023; 0.38 nmol, p = 0.015; 3.8 μmol, p = 0.002; and 38 μmol, p < 0.001; Figure 1B). These results suggest that mice were able to detect TMT from 3.8 pmol, since this amount induced a slight avoidance reaction (Figure 1B), but TMT was strongly avoided at pure concentration only as measured with both time spent in zones and avoidance ratio.

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