Wen-Yu Cao1,2, Zhao-Lan Hu1, Yang Xu3, Wen-Juan Zhang1, Fu-Lian Huang1, Xiao-Qing Qiao1, Yan-Hui Cui1, Wei Wan2, Xue-Qin Wang4, Dan Liu1, Ru-Ping Dai5, Fang Li6, Chang-Qi Li7. 1. Department of Anatomy and Neurobiology, School of Basic Medical Science, Central South University, Tongzipo Road 172, Changsha, Hunan, 410013, China. 2. Laboratory of Clinical Anatomy, University of South China, Hengyang, Hunan, China. 3. Institute of Neuroscience, Medical College, University of South China, Hengyang, Hunan, China. 4. Center for Experimental Medicine, The Third Xiangya Hospital, Central South University, Tongzipo Road 138, Changsha, Hunan, China. 5. Department of Anesthesia, the Second XiangYa Hospital, Central South University, Changsha, Hunan, China. 6. Department of Anatomy and Neurobiology, School of Basic Medical Science, Central South University, Tongzipo Road 172, Changsha, Hunan, 410013, China. fangli@csu.edu.cn. 7. Department of Anatomy and Neurobiology, School of Basic Medical Science, Central South University, Tongzipo Road 172, Changsha, Hunan, 410013, China. changqili@csu.edu.cn.
Abstract
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.
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.
Entities:
Keywords:
Environmental enrichment; Microglia; Social dominance tube test; Social hierarchy
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