| Research Abstract |
In the preparations of the lumbar sympathetic ganglion dissected from bullfrogs, the neural responses to electrical stimulation were monitored by using multiple-site optical recording of electrical activity,with a voltage- sensitive merocyanine-rhodanine dye (NK2761) and a multiple element photodiode array. Voltage-related absorbance changes evoked by nerve stimulation with depolarizing (positive) square current pulses using a suction electrode were recorded simultaneously from many contiguous loci in the preparation.
The optical signals, evoked by the antidromic stimulation for the post- synaptic axons of the ganglion cells (post-stimulation), exhibited a relatively simple shape with a sharp spike followed by the undershoot, which is likely to reflect the action potential and the after-hyperpolarization of the ganglion cells respectively. On the other hand, the optical signals, evoked by orthodromic stimulation applied to the pre-synaptic fibers (pre-stimulation), were also spike-like but more complex in shape, and the double-peaked signals were often observed, suggesting that the component from pre-synaptic neurons and that from post-synaptic neurons were superimposed in the evoked optical signals.
Using a low-Ca^<2+> Ringer solution or d-tubocurarine (d-Tc) to suppress the synaptic transmission, the optical signals evoked by pre-stimulation were successively separated into pre-synaptic and post-synaptic components. The pre- synaptic component of the optical signals was resistant to the suppression of the synaptic transmission, and was suggested to be dependent on the external Ca^<2+>.
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