DEVELOPMENT OF GLUTAMATE-STIMULATED PHOSPHATIDYLINOSITOL METABOLISM IN PRIMARY NEURONAL AND ASTROCYTE CULTURES

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