Exposure to xylene early in life induces memory abnormalities of adult male mice

Xylene, an aromatic hydrocarbon, is widely used as a solvent in industries, such as printing and rubber and leather manufacturing. Despite the significant industrial benefits of xylene, there are increasing concerns about its environmental and health impacts. However, the effects of early exposure to xylene on the central nervous system are poorly understood. Here, using novel and unique approach, we investigated the neurobehavioral effects of xylene using postnatal lactation C57BL/6N male mice (Mus musculus) exposed to 0 (control) or 2 different doses (2 or 20 ppm) of xylene for 7 consecutive days at 22 h/d. The concentrations of xylene used corresponded respectively to 40 and 400 times the indoor air quality standard in Japan. We examined the effects of xylene on the murine central nervous system using a battery of behavioral tests, comprising the open field test, light-dark transition test, and contextual-cued fear conditioning test at 12 weeks of age. We found that mice exposed to xylene (2 and 20 ppm) presented reduced spatial-associative or tone-cued associative memory in the contextual-cued fear conditioning test. In addition, immunohistochemical analysis revealed a decrease in doublecortin positive cells in the hippocampal dentate gyrus in the xylene exposure group compared with the control group. We confirmed that xylene exposure during postnatal lactation affects the formation of the neural circuit base and behavior in adulthood, suggesting that it is detrimental to postnatal brain development.