Abstract: Spatial distribution of spinal pre-EPSP(pre-EPSP)on the lateral dendrite was explored with multiple intracelluar recording technique in 8 Mauthner cells of the crucian carps. The results showed that pre-EPSPwith maximal amplitude was recorded at the soma, from where its amplitude decayed progressively along the lateral dendrite. The style of decay was very comparable to that of antidromic action potential. It is suggested that: ① The synapses mediating pre-EPSP are located densely at the soma; ② As the antidromic action potential, the pre-EPSP propagates along the lateral dendrite simply in the manner of electrotonic spread. It means that no synapses mediating pre-EPSP impinge on the lateral dendrite.

Key words: mauthner cell, spinal pre-EPSP, lateral dendrite, electrotonic spread, crucain carp