Fig. 1. Effects of naloxone on mechanical allodynia. Effects of spinal administration of naloxone on mechanical allodynia, as measured by withdrawal thresholds to von Frey stimulation. Doses ranged from 0 (saline) to 100 μg naloxone. Data are presented as percent of maximum possible effect (%MPE; mean ± SEM) of eight or nine rats each, 60 min after injection of naloxone. *P < 0.01 versus  saline.