Abstract: Direct stimulation of the olfactory nerves evoked a graded, complex excitory postsynap-tic potential (EPSP)on the Mauthner cell. The evoked EPSP was composed of two compo-nents with different characterastics. The latency of the first component was shorter with a average of 0. 62 ms and not sensitive to higher frequency stimulations. The second compo-nent closely followed the first one. It lasted more than 4 ms and presented a typical complex waveform. It was very sensitive to higher frequency stimulation; its amplitude declined by 40% while the stimulation interval shortened from 27 s to 100 ms.

Key words: Mauthner cell, olfactory nerve, EPSP, crucian carp