Fig. 3.

Effect of κ-ODN treatment on peripheral U 69,593 analgesia in the formalin flinch test. Formalin (50 μl, 2.5%) was injected into the dorsal surface of the rat hindpaw 10 min after the injection of drug or saline at the same site. A, Time course of formalin-induced flinching behavior for the different treatment groups exhibits a characteristic biphasic response. Data are summarized in B. One hundred nanomoles of the κ-ORA U 69,593 (U69) significantly blocked the formalin-induced second phase flinching response. The antinociceptive effects of U69 were blocked by KOR antisense, but not mismatch ODN treatment. Administration of κ-ODN alone did not affect the formalin response. *p < 0.05.