Fig. 2. N -Methyl amitriptyline in rat sciatic nerve blockade. A volume of 0.2 ml of various concentrations was injected via  the sciatic notch. Because this is a permanently charged drug, onset of block is accordingly relatively slow, but full nerve block was achieved by approximately 30 min. (A ) N -Methyl amitriptyline 5 mm (n = 7) revealed a time to full recovery of approximately 7 h. (B ) N -Methyl amitriptyline 10 mm (n = 7) revealed a time to full recovery of approximately 10 h. Although nociceptive blockade is more pronounced, no significant difference was found in motor blockade. (C ) N -Methyl amitriptyline 20 mm (n = 6): This concentration appears to be toxic, because three animals (50%) had residual neural blockade at day 4 and were euthanized. Please note the different time scale on the y  axis.