Fig. 1.

Diagram illustrating the experimental strategy to study the effects of KOR knock-down using antisense ODNs. Antisense ODN targeting the cloned rat KOR was administered intrathecally into the lumbosacral area twice daily (dosing interval 10–12 hr) for 4 consecutive days, each dose containing 12.5 μg of ODN in a 5 μl volume followed by a 10 μl saline flush. The efficacy of the antisense ODN treatment to cause a knock-down of the peripheral KOR was evaluated using the formalin test. Rats showing a block of the peripheral analgesic actions of the κ-ORAs in the formalin test were subsequently examined electrophysiologically to test κ-ORA modulation of visceral nociception.