Ba2+ does not support synaptic vesicle retrieval in rat cerebrocortical synaptosomes

To investigate whether any specific requirement for extracellular Ca2+ exists in the control synaptic vesicle retrieval, we examined the ability of the divalent cation Ba2+ to substitute for Ca2+ in both vesicle exocytosis and endocytosis. Ba2+ stimulated glutamate release from rat cerebrocortical synaptosomes. Ba2+-evoked release was inhibited by bafilomycin A1, indicating release was via exocytosis of synaptic vesicles. However, Ba2+ did not stimulate vesicle retrieval, monitored by a FM2-10-based retrieval assay. Therefore synaptic Vesicle retrieval in central nerve terminals has a specific requirement for extracellular Ca2+ and the Ca2+ receptor for retrieval has a different cation specificity to the Ca2+ receptor for exocytosis. (C) 1998 Elsevier Science Ireland Ltd. Ail rights reserved.