Phenol solutions differentially block conduction in cutaneous nerve fibers of the cat

The action of phenol in Tyrode solution on nerve conduction has been investigated in vivo in the desheathed sural nerve of cats. A section of 8 mm of the nerve was exposed to phenol solution. At low phenol concentrations (0.05-0.125%) a reversible block of A- and C-fibers occurred. At higher concentrations (0.6-1%) a selective and persistent C-fiber block could be achieved. The size of the residual A-volley was between 50% and 81% when all C-fibers were blocked.