| This study was designed to shed some light on the behavioral, physiological and gene expression changes of predator-naive Brandt’s voles (Lasiopodomys brandtii) exposed to predator and non-predator odors and to determine whether voles can differentiate between sympatric and allopatric predators. Also, in the present study we measured the behavioral, hormonal and neurobiological changes after repeated exposure to cat feces and found out which process will be triggered by repeated exposure between habituation and sensitization. Finally, we tried to discover the role of the intensity of the cat feces in the anti-predator responses (behavioral, endocrine and molecular changes) of Brandt’s voles. The following results were obtained:1-The behavioral, endocrine and CNS changes upon exposure to predator odor were found and the voles could innately and skillfully differentiate the odors from different species. The odors from sympatric predators triggered the higher responses than allopatric ones. During the10min odor presentation, animals tested with predator odors displayed significantly more avoidance (F4,86=5.265, P=0.001), concealing (F4;86=5.982,P=0.001), freezing behavior (except for snake group)(F4,86=4.976, P=0.001), jumping (F4,86=4.781, P=0.01) and vigilant rearing (F4,86=3.248, P=0.016), and significantly less contact time (F4,86=3.041,P=0.05) than the groups of non-predator’s odor. Head out (F4,86=2.298, P=0.213) and locomotion behaviors (F4,86=1.809, P=0.134) did not show significant changes among the tested groups. Within the predators group, weasel and cat groups showed significantly less and higher grooming behavior, respectively, than snake group (F4,86=3.067,P=0.05). Analysis of variance showed that both ACTH and CORT serum levels significantly increased when voles were subjected to the predator odors (F4,57=13.367, P=0.001and F4,57=15.81, P=0.05respectively). However,(odor×sex) interaction showed no effect on both ACTH and CORT serum levels. ACTH serum level of males Brandt’s voles was significantly higher than that of females (F1,57=6.403, P=O.05)(male was23.587±0.965and female was20.946±0.755). Moreover, Exposure to feces of different species significantly increased c-fos mRNA expression in the medial hypothalamic regions of tested voles (F4,80=42.642, P=0.001), the highest and lowest c-fos mRNA expression levels were observed in animals exposed to cat and goat feces, respectively.2-We found that the habituation and sensitization happened when Brandt’s voles were exposured to prolonged predator threat and they were complementary rather than contradictory in the anti-predator defensive responses. Voles exposed to cat feces in1Day and3Days groups displayed significant flight-related behaviors by showing more avoidance (F5,98=2.45, P=0.04), more concealing (F5,98=3.42, P=0.007), less contact time to the odor source (F5,98=6.62, P=0.001),higher freezing behavior (F5,98=5.54, P=0.001) higher locomotion behavior (F5,98=7.96, P=0.001) and vigilant rearing (F5,98=2.46, P=0.04) compared to the other treatment groups. A significant decrease in non-defensive grooming behavior (F5,98=8.52, P=0.001) was also observed. A non-significant head out (F5,98=0.76, P=0.58) and jumping (F5,98=1.51, P=0.19) behaviors were also measured. ACTH and corticosterone serum levels significantly increased when voles were subjected to the cat feces once (1Day) and for3consecutive days (3Days)(F5,95=7.79, P=0.001and F5,95=15.52, P=0.001respectively) than the other groups. Two-way ANOVA and post hoc test revealed that repeated exposure to cat feces for different periods significantly increased AfosB mRNA expression in the hypothalami of Brandt’s voles (F5,96=8.69, P=0.001) that the highest AfosB mRNA expression levels were quantified in voles exposed to cat feces for6and12consecutive days. Neither Sex (F5,96=0.07, P=0.934) nor (period x sex) interaction (F5,96=0.31, P=0.91) showed any significant effect on AfosB mRNA expression level.3-We summarized that the behavioral, hormonal and CNS changes were linked to the chemical constituents of cat feces and therefore they subsequently decreased when the cat feces were stored for longer durations. First day group showed strong defensive behavioral responses toward the freshly collected cat feces. During the10min odor presentation, animals tested with freshly collected feces (First day group) showed significant flight-related behaviors (avoidance (F4,91=8.014, P=0.001), Jumping (F4,91=3.042, P=0.022), less contact time (F4,91=3.029, P=0.022),higher concealing (F4,91=3.709, P=0.008) and more vigilance rearing (F4,91=5.634, P=0.001) compared to other treatment groups. Freezing behavior was significantly suppressed when the used cat feces became older (F4,91=7.604, P=0.001). Locomotion and Head out behaviors (F4,91=1.688, P=0.161andF4,91=0.288, P=0.885) showed a non-significant change among the tested voles. Howevera significant sex effect (F1,91=5.972, P=0.05) was observed that males showed longer bouts of locomotion than females (128.93±9.838and99.800±8.214respectively). ACTH and corticosterone serum levels significantly increased when animals were exposed to freshly collected feces (F4,91=16.513, P=0.001and F4,91=19.151, P=0.001respectively) that the first day group showed a distinctive higher endocrine responses than other groups which subsequently decreased when the stored feces came to be older. Two-way ANOVA and post hoc test disclosed that exposure to the freshly collected cat feces significantly increased c-fos mRNA expression in the medial hypothalamic region of Brandt’s voles (F4,80=46.126, P=0.001). The c-fos mRNA expression levels were found to decline upon exposure to older cat feces.The findings of the three experiments contribute to better understanding of the predator-prey interaction. The first experiment clarifies that Brandt’s voles respond maximally to the odors of predators and even within the predator group sympatric predators are mort fearful to the voles than the allopatric ones. In the second experiment we found that the behavioral and hormonal measurements gradually habituated to the repeated exposure of cat feces; however, the molecular parameters did not. Finally, the third experiments showed clearly that Brandt’s voles flexibly respond to the various degrees of the same threat which led to habituation of the measured parameters with low-threshold threat. |
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