Bauco P, Wang Y, Wise R A
Department of Psychology, Concordia University, Montreal, Que., Canada.
Brain Res. 1993 Jul 23;617(2):303-8. doi: 10.1016/0006-8993(93)91098-d.
Unilateral microinjections of morphine (2.5 micrograms/0.5 microliter) into the ventral tegmental area potentiated the rewarding effects of lateral hypothalamic brain stimulation, causing parallel leftward shifts of the functions relating response rate to stimulation frequency. Testing was repeated eight times with no evidence of reliable day-to-day changes either in the direction of sensitization or in the direction of tolerance to the reward-facilitating effects of the drug. The injection dose was sufficient to cause contraversive circling that continued long after the period of reward testing; as with the reward-facilitation, there was neither tolerance nor sensitization to this locomotor effect of the drug. The same dose given to control animals that were not tested for self-stimulation caused progressively stronger circling with repeated testing. Lack of sensitization of the reward-facilitating effects of ventral tegmental morphine raises the possibility of some degree of independence of the brain mechanisms of drug-induced locomotion and of reward-facilitation.
将吗啡（2.5微克/0.5微升）单侧微量注射到腹侧被盖区，可增强下丘脑外侧脑刺激的奖赏效应，使反应率与刺激频率之间的函数关系平行向左移动。该测试重复了八次，未发现药物奖赏促进效应的敏化或耐受方向存在可靠的每日变化证据。注射剂量足以引起对侧旋转，这种旋转在奖赏测试期结束后仍持续很长时间；与奖赏促进作用一样，对药物的这种运动效应既没有耐受也没有敏化。给予未进行自我刺激测试的对照动物相同剂量，随着测试的重复，会引起逐渐增强的旋转。腹侧被盖区吗啡奖赏促进效应缺乏敏化，这增加了药物诱导运动和奖赏促进的脑机制在某种程度上相互独立的可能性。
