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Background: Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by impaired social communication, poor social interactions and repetitive behaviors. The exact cause and mechanism of autism remains unknown. Both genetic and environmental factors may involve in ASD. In this study, we used diesel exhaust origin secondary organic aerosol (DE-SOA) as environmental pollutants. The aim of present study is to examine autism-like behaviors and related gene expressions in rats exposed to DE-SOA perinatally. Sprague-Dawley pregnant rats were exposed to clean air (control), diesel exhaust (DE) and DE-SOA in the exposure chamber for 5 h per day, 5days a week from gestational day 8 to postnatal day 21. At postnatal day 21, the male and female offspring rats were allocated into three different groups as follows: 1) rats exposed to clean filtered air; 2) rats exposed to DE; 3) rats exposed to DE-SOA. Social behaviors were investigated at 10~13-weeks-old rats using a 3-chambered social behavior test, social dominance tube test and marble burying test. Prefrontal cortex was collected under deep anesthesia to examine neurological and immunological markers, glutamate concentration, mast cell and microglia activation using real-time RT-PCR method, ELISA method and immunohistochemical analysis. Results: DE-SOA-exposed male and female rats showed poor sociability and social novelty preference, socially dominant behavior and increased repetitive behavior compared with the control rats. The mRNA expression levels of serotonin receptor (5-HT(5B)) and brain-derived neurotrophic factor (BDNF) were down-regulated whereas interleukin 1 b　(IL-b), and heme oxygenase 1 (HO-1) were upregulated in the prefrontal cortex of male and female rats exposed to DE-SOA compared to the control rats. In addition, the expression of mast cells and microglia marker ionized calcium-binding adapter molecule (Iba)1 were increased in the prefrontal cortex of male and female rats exposed to DE-SOA. Glutamate concentration was increased significantly in the prefrontal cortex of both male and female rats exposed to DE-SOA. Conclusion: Our results indicate that perinatal exposure to DE-SOA may induce autism-like behavior in rats by modulating neurological and immunological markers in the prefrontal cortex.

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