Fig. 8. The expression of EP1( A ), EP2( B ), and EP3( C ) receptors in the ipsilateral and contralateral lumbar dorsal horn 24 h after spinal nerve ligation (SNL) or sham surgery. Each bar represents the mean ± SEM of three to five animals. Asterisks indicate a significant difference from the corresponding sham control: ** P < 0.01, *** P < 0.001.