Behavioral responses to intramuscular formalin in AC1&8 DKO in comparison with wild-type mice. Cumulative response for each 5 min time is plotted on y axis as duration of responses. A. Comparison of nociceptive responses to intramuscular formalin in wild-type and AC1&8 DKO mice. Wild-type, n = 4 mice; AC1&8 DKO, n = 8 mice; B. Data from experiment A is grouped as early, intermediate and late phases in comparison with wild-type mice. p < 0.05. *Significant difference from wild-type mice.