Innate Fear under Social Hierarchy
Journal Title: The 1st Annual Meeting of Georgian Center for Neuroscience Research - Year 2020, Vol 2, Issue 20
Abstract
Behaviors are controlled by innate and learned mechanisms. Fear is a powerful emotion that greatly influences behaviors across species and can be induced by both innate and learned sensory inputs. In addition, fear-related behaviors with an elevated degree of complexity and subjectivity involve cognitive and emotional features and also different psychological and social characteristics. One of the important social characteristics across species is social hierarchy that profoundly impacts social survival, physical and mental health and reproductive success. The aim of this study was to investigate the relationship between social hierarchy and fear behaviors. For inducing social hierarchy, rats are kept together in a colony. The hierarchy usually develops within a few days and is stable as long as the group keeps together. In this study, for determining social hierarchy, dominance tube test was used, in which one mouse forces its opponent out backward from a narrow tube. Then, freezing, which is a characteristic behavior that is closely linked to fear, was investigated in male rats. It can be measured as the ratio of immobile time during a test period and is widely used as a quantitative marker for fear in various experimental paradigms. In our work, the rats were placed in an open-field test arena, a circular enclosure 50 cm in diameter and 50 cm high with the floor divided into 25 sections. The following responses were recorded over 10 minutes using a camera: the frequency and duration of defensive immobility (‘freezing’, is operationally defined as immobility accompanied by absence of other exploratory or defensive behaviors with at least two of the following autonomic reactions: urination; defecation; piloerection; exophthalmos). The results suggested that there was a significant difference between dominants and subordinates in their frequency and duration of defensive immobility. Subordinate rats exhibit more frequency and duration of defensive immobility as compared to dominant rats (P<0.01). Altogether, dominant rats exhibit a reactive innate-fear style characterized by increased proactivity with the environment, whereas subordinate rats exhibit a proactive innate-fear style characterized by immobility and passivity.
Authors and Affiliations
Mahshad Fadaeimoghadam Heydarabadi, Maryam Aboureihani Mohammadi, Soheila Hashemi, Roghaieh Khakpay, Soomaayeh Heysieattalab
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