Figure 2. (A) Initial phase of functional impairment, shown as a percentage of maximal possible effect (%MPE; mean +/- SE) after injection of 0.1 ml tetracaine (closed symbols, n = 8) or 0.1 ml N-butyl tetracaine (open symbols, n = 14), both at 37 mM in isotonic saline. The complete block induced by N-butyl tetracaine persisted for more than 24 h. Neurologic evaluation was performed before and at 5, 10, 30, 60, 120, and 180 min after injection of N-butyl tetracaine and before and at 5, 10, 30, 45, 60, 75, 90, 105, 120, and 180 min after injection of tetracaine. (B) The time course for recovery after N-butyl tetracaine injection, shown as %MPE (mean +/- SE; n = 9 to 14). Some rats were killed for morphologic examination. Neurologic evaluation was performed both at the times listed for part A and 24, 168, 336, 504, 840, 1,008, 1,176, and 1,344 h after injection of N-butyl tetracaine.