Kuhn D M, Greenberg I, Appel J B
J Pharmacol Exp Ther. 1976 Jan;196(1):121-7.
Pentazocine (10 mg/kg) and saline were used as discriminative stimuli in rats. After pentazocine administration, reinforcement could be obtained contingent on pressing one particular lever (left or right) in a two-lever operant chamber. Responding on the opposite lever was reinforced only after saline injections; a drug-lever combination was always held constant for each animal. Discriminated choice responding between pentazocine and saline was learned to an 80% correct criterion. Test injections of morphine produced dose-related responding on the pentazocine lever. Choice responding after 7.5 mg/kg of morphine was not significantly different from choice responding after 10 mg/kg of pentazocine. The discriminable ED50 values for both pentazocine and morphine were estimated from dose-response curves and when given in combination (pentazocine ED50 + morphine ED50), more drug-related responding occurred than occurred after either drug (ED50) alone. Naloxone produced saline-like responding but antagonized the stimulus properties of both pentazocine and morphine. However, the antagonism of the morphine cue by naloxone was significantly greater than the antagonism of the pentazocine cue. The results indicate that pentazocine and morphine are similar in at least one important respect suggesting that these drugs may share a common site of action.
喷他佐辛（10毫克/千克）和生理盐水被用作大鼠的辨别性刺激物。给予喷他佐辛后，在双杠杆操作性条件反射箱中按压一个特定杠杆（左或右）即可获得强化。只有在注射生理盐水后，对另一侧杠杆的反应才会得到强化；每种动物的药物-杠杆组合始终保持不变。以80%正确标准学会了对喷他佐辛和生理盐水的辨别性选择反应。吗啡的测试注射在喷他佐辛杠杆上产生了剂量相关的反应。7.5毫克/千克吗啡后的选择反应与10毫克/千克喷他佐辛后的选择反应没有显著差异。根据剂量-反应曲线估计了喷他佐辛和吗啡的可辨别半数有效剂量（ED50）值，当联合给药时（喷他佐辛ED50+吗啡ED50），与单独给予任何一种药物（ED50）相比，出现了更多与药物相关的反应。纳洛酮产生了类似生理盐水的反应，但拮抗了喷他佐辛和吗啡的刺激特性。然而，纳洛酮对吗啡线索的拮抗作用明显大于对喷他佐辛线索的拮抗作用。结果表明，喷他佐辛和吗啡在至少一个重要方面相似，这表明这些药物可能有共同的作用位点。
