Diluted phenol solution has been used to alleviate spasticity and to control pain since 1955. But the mechanism of nerve block with diluted phenol solution has not been established yet. Sciatic nerve of 46 rats were used to produce nerve block with phenol solution.

Nerve conduction studies before and after nerve block were done, and latency and amplitude of evokded potential were compared, Nerve block with pure alcohol and procaine solution were done and compared with those of diluted phenol solution.

The results were as following;

1) Nerve conduction after phenol block resulted in marked decrement of amplitude of the evoked potentials. Increased amount or increased concentration of phenol solution could produce more complete and permanent nerve block.

2) The degree of phenol nerve block was increased by increased concentration, amount of the solution or applying time of the solution to the nerve.

3) Nerve conduction after nerve block with pure alcohol resulted in decrement of amplitude of evoked potentials, while a little change in the conduction velocities. This results were suggestive of axon was affected more.

4) Nerve conduction after nerve block with procaine solution resulted in prolongation of latency and decrement of amplitude of evoked potentials. This results were suggestive of both compotents were affected.