Simon Nicholas W, Mendez Ian A, Setlow Barry
Department of Psychology, Texas A&M University, College Station, TX 77843-4235, USA.
Behav Neurosci. 2007 Jun;121(3):543-9. doi: 10.1037/0735-7044.121.3.543.
In this study, the authors examined the long-term effects of prior exposure to cocaine on a delay-discounting task commonly used to measure impulsive choice. Male Long-Evans rats received daily intraperitoneal injections of 30 mg/kg cocaine HCl or saline for 14 days. Following 3 weeks of withdrawal, rats began training. On each trial, rats were given a choice between 2 levers. A press on 1 lever resulted in immediate delivery of a single 45-mg food pellet, and a press on the other resulted in delivery of 4 pellets after a delay period. Impulsive choice was defined as preference for the small immediate over the large delayed reward. Three months after treatment, cocaine-exposed rats displayed increased impulsive choice behavior. They also showed less anticipatory responding (entries into the food trough) during the delays prior to reward delivery, indicating that the enhanced impulsive choice in these rats may be related to deficits in bridging the delay between response and reward. These data demonstrate that cocaine exposure can cause enduring increases in impulsive choice behavior, consistent with observations in human subjects with drug addictions.
在本研究中，作者研究了既往接触可卡因对常用于测量冲动性选择的延迟折扣任务的长期影响。雄性Long-Evans大鼠连续14天每天腹腔注射30mg/kg盐酸可卡因或生理盐水。在停药3周后，大鼠开始训练。在每次试验中，大鼠可在两个杠杆之间进行选择。按压一个杠杆会立即得到一粒45mg的食物颗粒，按压另一个杠杆则会在延迟一段时间后得到4粒食物颗粒。冲动性选择被定义为偏好小的即时奖励而非大的延迟奖励。治疗三个月后，接触可卡因的大鼠表现出冲动性选择行为增加。它们在奖励发放前的延迟期间也表现出较少的预期反应（进入食槽），这表明这些大鼠中增强的冲动性选择可能与在反应和奖励之间的延迟衔接方面的缺陷有关。这些数据表明，接触可卡因会导致冲动性选择行为持续增加，这与对药物成瘾的人类受试者的观察结果一致。
