Abstract: Direct stimulation of the crucian carp vagal lobe evoked two action potentials with different latencies in the Mauthner cell. One had a relatively long latency (0.4～0.5 ms). Stimulation of the vagal lobe at weak strength evoked a graded excitatory postsynaptic potential (EPSP). The other had a shorter latency (0.2～ 0.3 ms). Stimulation of the vagal lobe evoked directly an action potential. The results suggest that there might be a mutual nerve relationship between the vagal lobe and Mauthner cell. First ,there are inputs from the vagal lobe to Mauthner cell. Second ,there are inputs from Mauthner cell to the vagal lobe.

Key words: Mauthner cell, vagal lobe, action potential, crucian carp