DEPOLARIZATION-DEPENDENT SURVIVAL OF CEREBELLAR GRANULE CELLS ACCOMPANIED BY ACTIVATION OF Ca2+TURNOVER AND ENDOCYTOSIS . Department of Biology, Graduate School of Science, Osaka University, Osaka 560, Japan

KEIGO KOHARA, KEIKO TOMINAGA, AKIHIKO OGURA The rat cerebellar granule cells survive in vitro when maintained in a medium containing high concentration of KCl, but die when maintained under low KCl. We reported that both Ca2+ influx and Ca2+ efflux were activated under the high KC1 condition. Taking a possibility that an increased uptake of trophic factors might be resulted from high Ca 2+ turnover, we assayed the activity of endocytosis by uptaking rates of horseradish peroxidase and fluoresent dye FMl-43 applied extracellularly. The endocytotic aactivity was significantly higher under high KC1 condition.