A widely used red fluorescent dye for following synaptic activity by staining synaptic vesicles at the synapse or neuromuscular junctions. When used in combination with the green fluorescent dye SynaptoGreen™ (70020), synapses or neuromuscular junctions can be imaged independently in two colors. SynaptoRed™ has also been used to study endocytosis in Dictyostelia.