Effects of visual and olfactory density signals on social stress in Brandt's voles
ACTA THERIOLOGICA SINICA
2021, 41 (4):
Rodents have the density-dependent behavior-endocrine regulation mechanism.When their population density increases, it will increase social stress, nervous anxiety, aggression behaviors, as well as alter neuroendocrine in the brain.Social stress caused by increased density may involve different senses such as visual, olfactory, touch, hearing, andtaste, however, their distinct effects on social stress have never been evaluated.Our previous study indicates that high population density decreases the expression of oxytocin(OT) in the brain of male Brandt's voles(
Lasiopodomys brandtii), increases the expression of arginine-vasopressin(AVP), and increases serum corticosteroid(CORT), which are linked to the increase of aggressive behavior.However, the role of olfactory and visual signals in triggering social stress is unknown.Because the olfactory signal is involved in marking the territory or dominance of animals, while the visual signal is involved in collective cooperation for defending territory against intruders or predators, the social stress effects may be different.We used nest pads and mirrors to simulate olfactory and visual density.To test the distinct effects of olfactory and visual density signals on social stress of Brandt's voles, we analyzed the behavioral(open-field test, elevated plus-maze test, and three-chamber sociability test), body weight, organs, serum physiological indicators, and brain neurotransmitter expression changes.We found that nest-pads treatment groups with high olfactory density decreased OT expression but increased AVP expression in specific brain regions of Brandt's voles, which is similar to the density effect(except for the OT increase in males).This result generally supported the hypothesis that high-density olfactory is the main signal path of density-dependent social stress.High visual density group treatment increased OT expression in males, but decreased expression of glucocorticoid receptor(GR), serum adrenocorticotropic hormone(ACTH), and anxiety behavior in females, supporting the hypothesis that high-density visual is the main signal path for reducing social stress.Our study suggests that visual and olfactory signals play a different, or even opposite role in the density-dependent behavioral or population regulation of social Brandt's voles, which may be beneficial in maintaining an optimal population density or group size.
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