Imaging synaptic activity in intact brain and slices with FM1-43 in C-elegans, lamprey, and rat

The fluorescent probe FM1-43 has been used extensively for imaging vesicle recycling; however, high nonspecific adsorption resulting in elevated backg round levels has precluded its use in certain tissues, notably brain slices . We have found that a sulfobutylated derivative of beta-cyclodextrin (ADVA SEP-7) has a higher affinity for FM1-43 than the plasma membrane. ADVASEP-7 was used as a carrier to remove FM1-43 nonspecifically bound to the outer leaf let of the plasma membrane or extracellular molecules, significantly r educing background staining. This has enabled us to visualize synaptic vesi cle recycling in the nematode C. elegans, intact lamprey spinal cord, and r at brain slices.