Fig. 1.  Areas of anesthesia to pin prick on the plantar surface of six rats injected with 2% lidocaine (0.2 ml) at the ipsilateral sciatic nerve. Rats were placed on a wire grid and the skin of the paw probed with a sharp but nonpenetrating pin throughout the entire plantar surface. Probed areas that induced a brisk withdrawal of the leg are shown in white , and those for which no withdrawal occurred are shaded . The webs of skin between the toes were not probed. In five of six rats, the plantar region where the skin incision was made in the Brennan paw incision model was not anesthetized (see lower right paw diagram ). (Inset ) The locations of the test areas (medial, lateral, and central) and that of the incision in the lateral paw incision model are shown on this diagram of the plantar paw surface.