Fig. 6. One example of differential block of small myelinated and nonmyelinated fibers. Unitary responses of one Aδ fiber (conduction velocity = 5 m/s) and five C fibers (with conduction velocity ranging from 1.7 to 0.9 m/s) recorded from a microfilament of DRL5 before (control, upper trace) and at different times (shown at right of traces) after injection of lidocaine, 0.25%. Each trace is the average of three to five single successive records.