Schwartz Lindsay P, Kim Jung S, Silberberg Alan, Kearns David N
Psychology Department, American University, Washington, DC, United States.
Psychology Department, American University, Washington, DC, United States.
Drug Alcohol Depend. 2017 Sep 1;178:87-93. doi: 10.1016/j.drugalcdep.2017.04.031. Epub 2017 Jun 13.
Several recent studies have investigated the choice between heroin and a non-drug alternative reinforcer in rats. A common finding in these studies is that there are large individual differences in preference, with some rats preferring heroin and some preferring the non-drug alternative. The primary goal of the present study was to determine whether individual differences in how heroin or saccharin is valued, based on demand analysis, predicts choice.
Rats lever-pressed for heroin infusions and saccharin reinforcers on fixed-ratio schedules. The essential value of each reinforcer was obtained from resulting demand curves. Rats were then trained on a mutually exclusive choice procedure where pressing one lever resulted in heroin and pressing another resulted in saccharin. After seven sessions of increased access to heroin or saccharin, rats were reexposed to the demand and choice procedures.
Demand for heroin was more elastic than demand for saccharin (i.e., heroin had lower essential value than saccharin). When allowed to choose, most rats preferred saccharin. The essential value of heroin, but not saccharin, predicted preference. The essential value of both heroin and saccharin increased following a week of increased access to heroin, but similar saccharin exposure had no effect on essential value. Preference was unchanged after increased access to either reinforcer.
Heroin-preferring rats differed from saccharin-preferring rats in how they valued heroin, but not saccharin. To the extent that choice models addiction-related behavior, these results suggest that overvaluation of opioids specifically, rather than undervaluation of non-drug alternatives, could identify susceptible individuals.
最近的几项研究调查了大鼠在海洛因和非药物替代强化物之间的选择。这些研究中的一个常见发现是，偏好存在很大的个体差异，一些大鼠更喜欢海洛因，而一些则更喜欢非药物替代品。本研究的主要目的是根据需求分析确定海洛因或糖精的价值评估中的个体差异是否能预测选择。
大鼠在固定比率时间表上按压杠杆以获得海洛因注射和糖精强化物。从所得的需求曲线中获得每种强化物的基本价值。然后对大鼠进行互斥选择程序训练，按压一个杠杆会得到海洛因，按压另一个杠杆会得到糖精。在增加获取海洛因或糖精的机会七次后，大鼠再次接受需求和选择程序。
对海洛因的需求比糖精的需求更具弹性（即，海洛因的基本价值低于糖精）。当被允许选择时，大多数大鼠更喜欢糖精。海洛因的基本价值而非糖精的基本价值能预测偏好。在增加获取海洛因一周后，海洛因和糖精的基本价值均增加，但类似的糖精暴露对基本价值没有影响。增加获取任何一种强化物后，偏好都没有改变。
偏好海洛因的大鼠与偏好糖精的大鼠在对海洛因的价值评估方式上存在差异，但对糖精的评估方式没有差异。就选择模型与成瘾相关行为的程度而言，这些结果表明，阿片类药物的高估而非非药物替代品的低估可能识别出易感个体。
