Fig. 4. Injection of lidocaine and QX-314 close to the sciatic nerve produces a short complete sensory and motor block followed by a prolonged nociceptive-selective block. (A) Coinjection of lidocaine (0.5%, 1%, and 2%) and QX-314 (0.2%) produced a differential block since the block to a noxious pinch exceeds the short-duration motor deficit. (B) Lidocaine (0.5%, 1%, and 2%) injected alone produces a short-duration nonselective local anesthesia where nociceptive (closed squares) and motor (open squares) block have exactly the same duration. Grading for the nociceptive block is as in Fig. 3. Grading for motor block: 0 = baseline (115.8 g ± 2, n = 24), 1 = minimal block (50–100% of baseline); 2 = moderate block (less than 50% of baseline to 20 g); 3 = complete block, force less than 20 g (see Materials and Methods). (C) Summary of differential block produced after sciatic injection of 1% lidocaine alone and lidocaine coinjected with 0.2% QX-314.