Salamone J D, Steinpreis R E, McCullough L D, Smith P, Grebel D, Mahan K
Department of Psychology, University of Connecticut, Storrs 06269-1020.
Psychopharmacology (Berl). 1991;104(4):515-21. doi: 10.1007/BF02245659.
An important aspect of motivated behavior is that organisms will perform complex instrumental behaviors to gain access to stimuli such as food. In the present study, food-deprived rats were tested in an operant chamber in which the animals had a choice between pressing a lever to obtain a more-preferred food (Bioserve pellets), or free feeding on a less-preferred food (lab chow). Typically, rats pressed the lever to obtain the preferred food pellets, and ate little of the less-preferred food even though it was freely available. Pre-fed rats showed suppression of both lever pressing and feeding. Systemic administration of 0.1 mg/kg haloperidol (HP) led to a dramatic shift in the behavior of these rats, such that the number of lever presses was substantially reduced, but the amount of less-preferred food consumed showed a significant increase. This result occurred if the rats pressed a lever on either a CRF or FR5 schedule. Injection of 3.5-7.0 micrograms HP directly into the nucleus accumbens, or intra-accumbens injections of 6-hydroxy-dopamine, also decreased lever pressing for food and increased feeding on laboratory chow. Thus, interference with brain dopamine suppressed a highly active instrumental response for food, although the behavior of the animal was still directed towards food acquisition and consumption.
动机行为的一个重要方面是，生物体为了获取诸如食物等刺激，会表现出复杂的工具性动作。在本研究中，对饥饿的大鼠在一个操作性条件反射箱中进行测试，在这个箱子里，动物可以选择按压杠杆以获取更偏好的食物（Bioserve颗粒饲料），或者自由进食不太偏好的食物（实验室用饲料）。通常情况下，大鼠会按压杠杆来获取偏好的食物颗粒，即使不太偏好的食物可以自由获取，它们也很少吃。预先喂食的大鼠表现出杠杆按压和进食行为均受到抑制。全身注射0.1mg/kg氟哌啶醇（HP）导致这些大鼠的行为发生显著变化，即杠杆按压次数大幅减少，但不太偏好的食物摄入量显著增加。无论大鼠是按照CRF还是FR5模式按压杠杆，都会出现这种结果。向伏隔核直接注射3.5 - 7.0微克HP，或者向伏隔核内注射6 - 羟基多巴胺，也会减少为获取食物而进行的杠杆按压，并增加对实验室用饲料的进食量。因此，干扰大脑多巴胺会抑制对食物的高度活跃的工具性反应，尽管动物的行为仍然是朝着获取和消耗食物的方向。
