Niemann-Pick disease type C (NPC) is a progressive neurodegenerative disorder caused mainly by mutations of NPC 1 (95%).A biochemical hallmark of this disease is the intracellular accumulation of free cholesterol in lysosomes.In all cell types,neurons are most vulnerable to NPCl-deficiency.NPC1 is present not only in neuronal cell bodies,but also abundant in distal axons.The presence of NPC 1 in axons might indicate a neuron specific function of NPC 1 in addition to its classical role in lipid trafficking from late endosomes/lysosomes.In this paper,electrophysiological and fluorescent dye studies were performed on cultured hippocampal neurons to gain insight into the importance of NPC 1 in regulating synapse function of central nervous system.We found that initial synapse formation was unaffected by the NPC 1 deficient over the period examined.