Role of early environmental enrichment on the social dominance tube test at adulthood in the rat

• Published in: Psychopharmacology Vol. 234; no. 22; pp. 3321 - 3334
• Main Authors: Cao, Wen-Yu, Hu, Zhao-Lan, Xu, Yang, Zhang, Wen-Juan, Huang, Fu-Lian, Qiao, Xiao-Qing, Cui, Yan-Hui, Wan, Wei, Wang, Xue-qin, Liu, Dan, Dai, Ru-Ping, Li, Fang, Li, Chang-Qi
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.11.2017; Springer; Springer Nature B.V
• Subjects: Animals; Animals, Newborn; Biomedical and Life Sciences; Biomedicine; Blotting, Western; Brain; Calcium-Binding Proteins - metabolism; Competitive Behavior; DNA methyltransferase; Dominance; Dominance hierarchies; Enrichment; Female; Food; Foraging behavior; Hierarchy, Social; Hypothalamus; Hypothalamus - physiology; Immunohistochemistry; Male; Microfilament Proteins - metabolism; Microglia; Microglia - physiology; Neuroplasticity; Neurosciences; Observations; Original Investigation; Pharmacology/Toxicology; Physiological aspects; Psychiatry; Rats; Rats, Sprague-Dawley; Rodents; Social Behavior; Social Dominance; Social Environment; Social hierarchy; Social dominance tube test; Environmental enrichment; Social hierarchy; Microglia
• ISSN: 0033-3158; 1432-2072
• DOI: 10.1007/s00213-017-4717-3

Rationale Environmental enrichment (EE) could influence brain plasticity and behavior in rodents. Whether the early EE may predispose individuals to a particular social hierarchy in the social dominance tube test (SDTT) at adulthood is still unknown. Objective The present study directly investigated the influence of EE on competitive success in the SDTT among adult rats. Methods Male rats were maintained in EE from postnatal days 21 to 35. Social dominance behavior was determined by SDTT, competitive food foraging test, and mate preference test at adulthood. IBA-1 expression in the hypothalamus was examined using immunohistochemistry and western blot. Results EE rats were prone to become submissive during a social encounter with standard environment (SE) rats in the SDTT. No difference was found in food foraging in the competitive food foraging test between SE and EE rats. Male EE rats were more attractive than the SE to the female rats in the mate preference test. IBA-1 expression was found to be decreased in the hypothalamus of EE rats compared to SE group. Infusion of a microglia inhibitor reduced percentage of forward in SE rats in the SDTT. Infusion of DNA methyltransferase inhibitor prevented the development of subordinate status in EE rats and restored the expression of IBA-1 in the hypothalamus. Conclusions The results suggest that early EE did not lead to reduced social hierarchy in the male rat. However, EE caused a reduction in the percentage of forward in the SDTT, which might be associated with reduced number of microglia in the hypothalamus.