Abstract：
In an animal model of compulsive drug use, a subset of rats continues to self-administer cocaine despite footshock consequences and is considered punishment resistant. We recently found that punishment resistance is associated with habits that persist under conditions that typically encourage a transition to goal-directed control. Given that random ratio (RR) and random interval (RI) schedules of reinforcement influence whether responding is goal-directed or habitual, we investigated the influence of these schedules on punishment resistance for cocaine or food. Male and female Sprague Dawley rats were trained to self-administer either intravenous cocaine or food pellets on a seeking-taking chained schedule of reinforcement, with the seeking lever requiring completion of either an RR20 or RI60 schedule. Rats were then given four days of punishment testing with footshock administered at the completion of seeking on a random one-third of trials. For cocaine-trained rats, the RI60 schedule led to greater punishment resistance (i.e., more trials completed) than the RR20 schedule in males and females. For food-trained rats, the RI60 schedule led to greater punishment resistance (i.e., higher reward rates) than the RR20 schedule in female rats, although male rats showed punishment resistance on both RR20 and RI60 schedules. For both cocaine and food, we found that seeking responses were suppressed to a greater degree than reward rate with the RI60 schedule, whereas response rate and reward rate were equally suppressed with the RR20 schedule. This dissociation between punishment effects on reward rate and response rate with the RI60 schedule can be explained by the nonlinear relation between these variables on RI schedules, but it does not account for the enhanced resistance to punishment. Overall, the results show greater punishment resistance with the RI60 schedule as compared to the RR20 schedule, indicating that schedules of reinforcement are an influencing factor on resistance to negative consequences.
摘要：
在强迫性用药的动物模型中,尽管有脚部电击的后果，但仍有一部分大鼠继续自我服用可卡因，并被认为是抗惩罚的。我们最近发现，抵制惩罚与在通常鼓励向目标导向控制过渡的条件下持续存在的习惯有关。鉴于随机比率（RR）和随机间隔（RI）强化计划影响响应是目标导向的还是习惯性的，我们调查了这些时间表对可卡因或食物的惩罚抵抗的影响。对雄性和雌性SpragueDawley大鼠进行了自我训练，可以按照寻求补强链的时间表对静脉注射可卡因或食物颗粒进行自我管理，寻找杠杆需要完成RR20或RI60时间表。然后对大鼠进行为期四天的惩罚测试，并在随机三分之一的试验中完成搜索后进行脚部电击。对于受过可卡因训练的老鼠，RI60时间表导致更大的惩罚阻力(即，在男性和女性中完成的试验)比RR20时间表更多。对于受过食物训练的老鼠来说，RI60时间表导致更大的惩罚阻力(即，更高的奖励率)比雌性大鼠的RR20时间表，尽管雄性大鼠在RR20和RI60时间表中均显示出惩罚抗性。对于可卡因和食物，我们发现，在RI60时间表中，寻求响应受到的抑制程度大于奖励率，而RR20方案的缓解率和奖励率同样受到抑制。RI60时间表对奖励率和响应率的惩罚效果之间的这种分离可以通过RI时间表上这些变量之间的非线性关系来解释，但这并不能解释对惩罚的抵抗力增强。总的来说,结果表明，与RR20时间表相比，RI60时间表具有更大的惩罚抵抗力，表明加固时间表是抵抗负面后果的影响因素。
