Primary neurons from rodent brain hippocampus and cortex have served as important tools in biomedical research over the years. However, protocols for the preparation of primary neurons vary, which often lead to conflicting results. This report provides a robust and reliable protocol for the production of primary neuronal cultures from the cortex and hippocampus with minimal contribution of non-neuronal cells. The neurons were grown in serum-free media and maintained for several weeks without any additional feeder cells. The neuronal cultures maintained according to this protocol differentiate and by 3 weeks develop extensive axonal and dendritic branching. The cultures produced by this method show excellent reproducibility and can be used for histological, molecular and biochemical methods.

7Primary neurons from rodent brain hippocampus and cortex has served as great tools in biomedical 8 research over the years. However, protocols for the preparation of primary neurons vary, which often 9 leads to conflicting results. This report provides a robust and reliable protocol for the production of 10 primary neuronal cultures from the cortex and hippocampus with minimal contribution of non-11 neuronal cells. The neurons were grown in serum free media and maintained for several weeks 12 without any additional feeder cells. The neuronal cultures maintained according to this protocol 13 differentiate and by three weeks develop extensive axonal and dendritic branching. The cultures 14 produced by this method show excellent reproducibility and can be used for histological, molecular 15 and biochemical methods. 16 17

Brain-derived neurotrophic factor (BDNF) is a neurotrophin essential for neuronal survival and differentiation. We examined the concentration of BDNF in cord serum from newborns exposed to methylmercury (MeHg) and polychlorinated biphenyls (PCB) in utero by maternal consumption of whale meat. The cohort consisted of 395 singleton births (206 boys and 189 girls), gestational age ranging from 38 to 42 weeks. Serum BDNF was measured by sandwich ELISA. Maternal smoking habits and other relevant factors were obtained by interviewing the mothers. The exposure to MeHg was estimated from Hg concentrations in cord blood, whereas exposure to PCB was estimated based on maternal serum concentrations. Only MeHg exposure affected the serum BDNF, which decreased in a concentration-dependent manner in girls born to nonsmoking mothers. Maternal smoking significantly increased BNDF in girls but not in boys. For further statistical analyses, we used the serum BDNF concentration as a continuous outcome variable in supervised regression models. Serum BDNF concentration increased with gestational age, increased by maternal smoking, decreased slightly with MeHg exposure, and maternal smoking enhanced the decrease in serum BDNF induced by MeHg exposure. Cord blood BDNF has been reported to increase in association with perinatal brain injuries and has been proposed as a possible predictive marker of neurodevelopmental outcomes. The negative effect that MeHg seems to exert on cord blood BDNF concentration could endanger compensatory responses to an adverse impact and therefore deserves attention.