Optical monitoring of the neural activity evoked by mechanical stimulationin the earthworm nervous system with a fluorescent dye, FM1-43

In the centra I nervous system of the earthworm, sensory and motor neurons have direct synapses on th ree giant fibers. To determine the locations of synapses and neural network activated by mechanical stimuli, we optically m onitored the activity-dependent staining in the earthworm ventral nerve cor d with a styryl dye, N-(3-triethylammoniumpropyl)-4-(4-(dibutylamino)styryl )pyridinium dibromide (FM1-43), and a confocal laser scanning microscope. W hen scratch stimulus was applied to the body wall of the earthworm, bright fluorescent spots with 3-10 mu m in diameter localized only in the stimulat ed segmental ganglion of the ventral nerve cord. The fluorescent intensity of these spots decreased during dye-free high K+ saline incubation. These r esults suggest that FM 1-43 is useful for activity-dependent staining of in vertebrate neurons and their synaptic regions as well as vertebrate nervous system. (C) 1999 Published by Elsevier Science Ireland Ltd. All rights res erved.