Department of Psychology, Rutgers University, 101 Warren Street, 301 Smith Hall, Newark, NJ 07102, USA.
Psychopharmacology (Berl). 2012 Oct;223(3):361-70. doi: 10.1007/s00213-012-2724-y. Epub 2012 May 5.
Repeated exposure to psychostimulants alters behavioral responses to reward-related cues; however, the motivational underpinnings of this effect have not been fully characterized.
The following study was designed to examine how amphetamine sensitization affects performance in rats on a series of Pavlovian and operant tasks that distinguish between general-incentive and outcome-selective forms of conditioned responses.
Adult male rats underwent Pavlovian and instrumental training for food pellet rewards. Following training, rats were sensitized to D-amphetamine (2 mg/kg for 7 days). Rats were subsequently tested on an outcome-selective Pavlovian-instrumental transfer (PIT) task, an outcome-reinstatement task, and an outcome devaluation task. Additionally, in a separate experiment, PIT was assessed in amphetamine-sensitized and control rats using a Pavlovian backward-conditioned stimulus.
Repeated amphetamine exposure sensitized locomotor activity to acute amphetamine challenge. Amphetamine altered responses to CS presentations by increasing conditioned approach. During tests of PIT, amphetamine-treated rats showed no outcome-selectivity in their responding, responding to a CS whether or not it shared a common outcome with the instrumental response. No effect of amphetamine sensitization was observed on tests of outcome-selective reinstatement by outcome delivery or action selection based on outcome value. Amphetamine-sensitized rats showed impaired outcome-selective PIT to a backward CS but were unaltered in conditioned approach.
Amphetamine sensitization prevents outcome-selective responding during PIT, which is dissociable from amphetamine's effects on conditioned approach. These data suggest fundamental alterations in how stimuli motivate action in addiction.
反复接触精神兴奋剂会改变与奖励相关线索的行为反应；然而，这种效应的动机基础尚未完全描述。
本研究旨在探讨安非他明敏化如何影响大鼠在一系列条件反射任务中的表现，这些任务区分了一般激励和结果选择的条件反应形式。
成年雄性大鼠接受食物丸奖励的条件反射和工具训练。在训练结束后，大鼠被敏化到 D-安非他明（7 天 2 毫克/公斤）。然后，大鼠接受结果选择条件反射-工具转移（PIT）任务、结果恢复任务和结果贬值任务的测试。此外，在一个单独的实验中，使用条件反射的反向条件刺激评估了敏化和对照大鼠的 PIT。
重复安非他明暴露使急性安非他明挑战的运动活动敏化。安非他明通过增加条件接近来改变对 CS 呈现的反应。在 PIT 测试中，安非他明处理的大鼠在反应中没有表现出结果选择性，无论 CS 是否与工具反应具有共同的结果，都会对其作出反应。在基于结果价值的结果传递或动作选择的结果选择性恢复测试中，没有观察到安非他明敏化的影响。安非他明敏化大鼠对反向 CS 的 PIT 表现出受损的结果选择性，但对条件接近没有改变。
安非他明敏化阻止了 PIT 期间的结果选择性反应，这与安非他明对条件接近的影响不同。这些数据表明，在成瘾中，刺激激发行动的方式发生了根本的改变。
