Diller James W, Saunders Benjamin T, Anderson Karen G
West Virginia University, Morgantown. WV 26506, United States.
Pharmacol Biochem Behav. 2008 Jun;89(4):546-55. doi: 10.1016/j.pbb.2008.02.008. Epub 2008 Feb 12.
Delay to presentation is one variable that can weaken the reinforcing efficacy of an outcome in a choice situation and drugs have been shown to modify such choices. A growing body of literature has examined effects of stimulant drugs on temporal (delay) discounting, but effects of caffeine, the most widely used stimulant in the world, have not previously been assessed. In the present experiment, effects of caffeine (administered acutely and repeatedly) on temporal discounting were analyzed. Male Sprague-Dawley rats (n=7) chose between a single food pellet delivered immediately after a lever press and three food pellets delivered after a delay. The delay to the three pellets increased within each session, from 0 to 16 s. High doses of caffeine increased large-reinforcer choice relative to control conditions. With repeated caffeine exposure, percent choice for the large reinforcer decreased relative to acute administration, but was still greater than pre-drug baseline. Following withdrawal of drug administration, choice returned to levels seen during pre-drug baseline. Reintroduction of caffeine increased the percent choice for a larger, delayed reinforcer to near acute levels. The results from the present study are consistent with previous research in which stimulant drugs have decreased temporal (delay) discounting.
就诊延迟是一个可能会削弱选择情境中结果强化效力的变量，并且已有研究表明药物会改变此类选择。越来越多的文献研究了兴奋剂药物对时间（延迟）折扣的影响，但此前尚未评估世界上使用最广泛的兴奋剂咖啡因的影响。在本实验中，分析了咖啡因（急性和反复给药）对时间折扣的影响。雄性斯普拉格-道利大鼠（n = 7）在按压杠杆后立即给予的一粒食物颗粒和延迟后给予的三粒食物颗粒之间进行选择。每次实验中，延迟给予三粒食物颗粒的时间从0秒增加到16秒。与对照条件相比，高剂量咖啡因增加了对大强化物的选择。随着咖啡因的反复给药，相对于急性给药，对大强化物的选择百分比有所下降，但仍高于给药前的基线水平。停止给药后，选择恢复到给药前基线时的水平。重新给予咖啡因可使对更大、延迟强化物的选择百分比增加至接近急性给药时的水平。本研究结果与之前关于兴奋剂药物减少时间（延迟）折扣的研究一致。
