Opioid 수용체 효능제의 뇌실 내 주입이 고양이 척수후각세포의 활성에 미치는 영향

Differential Actions of Intracerebroventricular Opioid Receptor Agonists on the Activity of Dorsal Horn Neurons in the Cat Spinal Cord

Intracerebroventricular (ICV) infusion of morphine (MOR) produces strong analgesia in man and animals. The analgesic effect is thought to be mediated by the centrifugal inhibitory control. But neural mechanisms of the analgesic effect of ICV morphine are not well understood. In the present study, we found that ICV MOR had dual actions on the activity of dorsal horn neurons: it produced both inhibition and excitation of dorsal horn neurons. Since MOR exerts its action via three different types of opioid receptors, we further sought to investigate if there are differential effects of opioid receptor agonists on dorsal horn neurons of the spinal cord in the cat. ICV VOR inhibited, excited and did not affect the heat responsers of dorsal horn neurons. ICV DAMGO and DADLE, mu-and delta-opioid agonist, respectively, exhibited the excitation of dorsal horn neurons. In contrast, U-50488, a k-opioid agonist, exhibited both the inhibition and excitation of dorsal horn neurons. These results suggest that opioid receptors have different actions on activity of dorsal horn neuron and that the inhibitory action of k-opioid agonist may subserve the analgesia often produced by ICV MOR.