PKCδ contributes to the generation of ongoing spontaneous pain in NTG-treated mice. (A) In response to repeated administration of NTG, ongoing spontaneous pain was developed in PKCδ wild-type (+/+) mice, but not in mice lacking PKCδ (−/−). (B) Difference score analysis confirmed that wild type, but not PKCδ null mice showed CPP to α-CGRP (8-37) after chronic NTG treatment. (C) Both wild type and PKCε null mice had CPP to α-CGRP (8-37) after chronic NTG treatment. (D) Difference score analysis showed chronic NTG treatment produced ongoing spontaneous pain in both PKCε null and wild type mice. * P < 0.05, *** P < 0.001, n = 6.