Fig. 3. The effect of prostaglandin E²(PGE²) on glutamate release from lumbar slices of naive, sham-operated, or nerve-ligated rats (  A ), and thoracic slices from nerve-ligated or lumbar slices from sham-operated rats (  B ), 3 days after surgery. Each  point represents the mean ± SEM of at least 5 animals (4–12 slices/dose).  Asterisks indicate a significant difference between spinal nerve–ligated, sham-operated, and/or naive animals (*  P < 0.05, ***  P < 0.001) at the corresponding PGE²concentration.  Daggers indicate a significant difference between naive and sham-operated animals after treatment with arachidonic acid (†  P < 0.05, †††  P < 0.001).  Double daggers indicate a significant difference between the PGE²-treated and vehicle-treated slices at the corresponding PGE²concentration (‡  P < 0.05, ‡‡  P < 0.01, ‡‡‡  P < 0.001).