中脑导水管周围灰质和海马在ACTH镇痛中的相互关系

THE RELATION OF PERIAQUEDUCTAL GRAY AND HIPPOCAMPUS IN THE ANALGESIA OF ACTH IN RATS

以往工作发现，中脑导水管周围灰质（ＰＡＧ）和海马在非阿片肽ＡＣＴＨ痛觉调制中占有重要地位。但它们之间的相互影响在ＡＣＴＨ痛觉调制中的作用，尚未阐明。本工作利用免疫组织化学和病阈测定方法，进一步观察大鼠ＰＡＧ和海马在ＡＣＴＨ镇痛时的相互关系，并与吗啡镇痛作用相比较。结果如下：（１）海马内注射ＡＣＩＨ（０．５ｕ／４μｌ）或吗啡（５μｇ／４μｌ），痛阈明显升高（１１９．３±４．７％，１２２．７±２６．８％）与对照组比较有显著差异（Ｐ＜０．０１），该明显效应均可被ＰＡＧ内注射阿片受体拮抗剂纳络酮所阻断；（２）ＰＡＧ内注射吗啡或ＡＣＴＨ后病阈提高更显著（１８０．９±５０．３％，２１９．８±７７．０％，Ｐ＜０．０１），但海马内注射纳络酮可阻断前者的效应（Ｐ＜０．０５）而对后者却无影响（Ｐ＞０．０５）；（３）伤害性刺激福尔马林（Ｆ）可诱发大鼠脊髓腰膨大背角原癌基因ｃ－ｆｏｓ显著表达，以Ⅰ、Ⅱ层较显著，海马或ＰＡＧ内注射ＡＣＴＨ均可抑制其背角ｃ－ｆｏｓ表达。结果提示：ＰＡＧ、海马均参与ＡＣＴＨ和阿片系统对脊髓痛信息传递的调制作用，在ＡＣＴＨ痛觉调制作用中，表明ＰＡＧ、海马之间的相互影响是复杂的。

It was found previously that the periaqueductal gray(PAG) and hippocampus play important roles in pain modulation of ACTH, a non-opiate peptide. The interaction between the PAG and hippocampus, however, was not clear in pain modulation of ACTH. In this experiment, using immunohistochemistry and measurement of pain threshold, we observed in rats the interrelationship of PAG and hippocampus in the analgesia effect of ACTH, and compared with that of morphine. The results showed: (1) The pain threshold was increased (119.3±4.7%, 122.7±26.8%) by intra-hippocampus injection of ACTH (0.5u/ 4μl) or morphine (5μg/ 4μl), as compared with the control group. The above-mentioned effects could be blocked by intra-PAG infection of naloxone, a blocker of opiate receptor. (2) The pain threshold was markedly increased by intra-PAG injection of ACTH or morphine (180.9±50.3%, 219.8%±77.0%). The effect of morphine could be blocked by intra-hippocampus injection of naloxone but not ACTH. (3) c-fos oncogene expression could be evoked by noxious stimulus (formalin, F) were densely distributed in the laminae Ⅰ、Ⅱ of the ipsilateral lumbar spinal dorsal horn, and inhibited by intra-hippocampus or intra-PAG injection of ACTH. The results showed that PAG and hippocampus participated in effects of ACTH and opiate system on pain modulation of spinal cord, indicating that the intfrachve influence between the PAG and hippocampus in pain modulation of ACTH is complicate.