Development of glutamate‐stimulated phosphatidylinositol metabolism in primary neuronal and astrocyte cultures

It was the purpose of the present study to evaluate glutamate-stimulated phosphatidylinositol metabolism in primary mixed astrocyte/neuron and neuron-enriched cortical cultures through different stages of development in vitro. Glutamate (0-200 microM) stimulated inositol phosphate accumulation in a concentration-dependent fashion at 6, 13 and 20 days in vitro. Pure astrocyte cultures exhibited glutamate-stimulated phosphatidylinositol hydrolysis only at high concentrations (100-400 microM), indicating that these cells contribute little to the overall inositol phosphate accumulation measured in mixed neuronal cultures treated with low glutamate concentrations. Comparison of mixed neuronal cultures with and without antimitotic treatment revealed that increasing astrocyte number suppressed glutamate-stimulated responses, presumably via glutamate uptake. In contrast to previous reports, glutamate-stimulated inositol phosphate accumulation, when expressed as a function of cell number, increased with increasing days in vitro.