Giordano J, Barr G A
Brain Res. 1987 Apr;429(2):247-53. doi: 10.1016/0165-3806(87)90105-2.
Patterns of morphine- and ketocyclazocine-induced analgesia in limb withdrawal and tail-flick tests of thermal and mechanical nociception were examined in the preweanling rat. In the forepaw test, morphine was more effective than ketocyclazocine with both thermal and mechanical stimuli. Both drugs first induced analgesia between 3 and 5 days of age. In the tail-flick test, ketocyclazocine-induced analgesia preceded morphine's effects against both thermal and mechanical stimuli by several days. Ketocyclazocine produced robust analgesia between 7 and 10 days of age, while the effects of morphine did not peak until day 14. In the hindpaw, morphine was more effective than ketocyclazocine against a higher intensity mechanical stimulus, while ketocyclazocine was more effective against a lower intensity mechanical stimulus. Morphine-induced analgesia was reversed by lower doses of naloxone than was ketocyclazocine-induced analgesia, regardless of body part tested, against all noxious stimuli. These findings demonstrate differences in morphine- and ketocyclazocine-induced analgesia that are dependent upon age, body topography, stimulus type and intensity and imply different physiologic roles of mu- and chi-opioid receptors in analgesia.
在断奶前大鼠的热痛觉和机械痛觉的肢体退缩及甩尾试验中，研究了吗啡和酮环佐辛诱导的镇痛模式。在前爪试验中，对于热刺激和机械刺激，吗啡比酮环佐辛更有效。两种药物均在3至5日龄时首次诱导出镇痛作用。在甩尾试验中，酮环佐辛诱导的镇痛作用比吗啡对热刺激和机械刺激的作用提前数天出现。酮环佐辛在7至10日龄时产生强烈的镇痛作用，而吗啡的作用直到第14天才达到峰值。在后爪试验中，对于较高强度的机械刺激，吗啡比酮环佐辛更有效，而对于较低强度的机械刺激，酮环佐辛更有效。无论测试身体部位如何，针对所有有害刺激，吗啡诱导的镇痛作用被纳洛酮逆转所需的剂量比酮环佐辛诱导的镇痛作用所需的剂量更低。这些发现表明，吗啡和酮环佐辛诱导的镇痛作用存在差异，这些差异取决于年龄、身体部位、刺激类型和强度，并暗示μ-阿片受体和κ-阿片受体在镇痛中具有不同的生理作用。
