Effects of docosahexaenoic acid on the survival and neurite outgrowth of rat cortical neurons in primary cultures

Effects of docosahexaenoic acid (DHA) on survival and neurite outgrowth were investigated in primary cultures of rat cortical neurons. Cell cultures were prepared from cortex on embryonic day 18 (E-18) for treatment with a series of DHA concentrations (12.5, 25, 50, 75, 100 and 200 μM). Docosahexaenoic acid (25-50 μM) significantly enhanced neuronal viability, but lower concentration of DHA (12.5 μM) did not show an obvious effect. In contrast, higher concentrations of DHA (100-200 μM) exerted the significant opposite effects by decreasing neuronal viability. Furthermore, treatment with 25 μM DHA significantly prevented the neurons from death after different culture days in vitro (DIV). Moreover, measurements from the cultures exposed to 25 μM DHA immediately after plating showed significant increases in the percentage of cells with neurites, the mean number of neurite branches, the total neuritic length per cell and the length of the longest neurite in each cell after 24 and 48 h in vitro (HIV). The DHA-treated neurons had greater growth-associated protein-43 (GAP-43) immunoactivity and higher phosphatidylserine (PS) and phosphatidylethanolamine (PE) contents, but lower phosphatidylcholine (PC) content than control neurons. The significant increased DHA contents were also observed in both PE and PS in the treated neurons. These findings suggest that optimal DHA (25 μM) may have positive effects on the survival and the neurite outgrowth of the cultured fetal rat cortical neurons, and the effects probably are related to DHA-stimulating neuron-specific protein synthesis and its enhancing the discrete phospholipid (PL) content through enrichment of DHA in the PL species.