Abstract
Repeated experience of winning in a social conflict setting elevates levels of aggression and may lead to violent behavioral patterns. Here, we use a paradigm of repeated aggression and fighting deprivation to examine changes in behavior, neurogenesis, and neuronal activity in mice with positive fighting experience. We show that for males, repeated positive fighting experience induces persistent demonstration of aggression and stereotypic behaviors in daily agonistic interactions, enhances aggressive motivation, and elevates levels of anxiety. When winning males are deprived of opportunities to engage in further fights, they demonstrate increased levels of aggressiveness. Positive fighting experience results in increased levels of progenitor cell proliferation and production of young neurons in the hippocampus. This increase is not diminished after a fighting deprivation period. Furthermore, repeated winning experience decreases the number of activated (c-fos-positive) cells in the basolateral amygdala and increases the number of activated cells in the hippocampus; a subsequent no-fight period restores the number of c-fos-positive cells. Our results indicate that extended positive fighting experience in a social conflict heightens aggression, increases proliferation of neuronal progenitors and production of young neurons in the hippocampus, and decreases neuronal activity in the amygdala; these changes can be modified by depriving the winners of the opportunity for further fights.
Highlights
Aggressive behavior helps to ensure survival, provides advantage in competition, and communicates social status (Scott, 1971)
We demonstrate that prolonged positive fighting experience increases proliferation of neuronal progenitors and neurogenesis in the DG of adult males
After 21 days of agonistic interactions accompanied by positive fighting experience, winners of all four examined mouse lines demonstrated aggressive behavior in agonistic interaction test, attesting to the robustness of the experimental approach
Summary
Aggressive behavior helps to ensure survival, provides advantage in competition, and communicates social status (Scott, 1971). Male rodents with a prior record of winning in a social conflict setting attack more frequently and may develop violent behavior patterns with little regard to the submissive signals of the opponent or to an unfamiliar environment (Van de Poll et al, 1982; Kudryavtseva et al, 2004; Kudryavtseva, 2006; Natarajan et al, 2009; Natarajan and Caramaschi, 2010). Mice that have won a series of fights in a social conflict paradigm display aggressive and hostile behavior (attacks, threats, and indirect aggression) even toward a much heavier and stronger male, a juvenile, a female, or a defeated conspecific demonstrating overt signs of submissiveness (Kudryavtseva, 2006). If winner animals are denied opportunities to engage in further fights for 2–3 weeks, they demonstrate a level of aggression higher than before deprivation (Kudryavtseva, 2006; Kudryavtseva et al, 2011)
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