Optical monitoring of synaptic transmission in bullfrog sympathetic ganglia using a voltage-sensitive dye.

Multiple-site optical recording of neural activity, using a voltage-sensitive merocyanine-rhodanine dye (NK2761) and a 12 x 12-element photodiode array, was employed to monitor the synaptic transmission in the bullfrog lumbar sympathetic ganglion. When the presynaptic nerve fibers were stimulated, the signals had two or three peaks, and their later phase was reduced in a low calcium bathing solution or in a solution containing D-tubocurarine. We conclude that the first phase of the optical signals evoked by the presynaptic stimulation corresponds to the electrical activity of the presynaptic neurons. The signals evoked by the postsynaptic stimulation showed relatively simple shape reflecting the action potential in the ganglion cells.