Abstract: Spatial distribution of the spinal pre-EPSP(pre-EPSP)and the antidromic action potential evoked by the stimulation of the spinal cord on the soma and ventral dendrite of the crucian carp Mauthner cell was explored by means of multiple intracellular recording technique. The results showed that the maximum amplitude of the pre-EPSP was recorded at the soma, it declined progressively along the ventral dendrite with a spatial constant of about 500 μm, a value much larger than 330 μm estimated on the basis of measurements of the antidromic action potential spreaded in the same direction as pre-EPSP. It suggested that the synapses mediated the pre-EPSP densely impinge on the regions near the soma, whereas scattered synapses also distribute along the ventral dendrite.

Key words: Mauthner cell, ventral dendrite, spinal pre-EPSP, synapse, spatial constant, crucian carp