Kosten Therese A, Zhang Xiang Yang, Haile Colin N
Michael E. DeBakey Veterans Affairs Medical Center, Houston, TX 77030, USA.
Behav Neurosci. 2007 Apr;121(2):380-8. doi: 10.1037/0735-7044.121.2.380.
The authors previously demonstrated that Fischer 344 (F344) and Lewis inbred rats differ in acquisition of cocaine self-administration. Other studies show that acquisition and maintenance of drug self-administration are predicted by locomotor activity in a novel environment among outbred Sprague-Dawley rats. The present study was designed to determine whether this relationship extended to F344 and Lewis rats. In Experiment 1, F344, Lewis, and Sprague-Dawley rats were trained to self-administer cocaine and tested with several doses under fixed- and progressive-ratio schedules of reinforcement. Self-administered infusions and ineffective active lever presses--those emitted during infusion and time-out periods--were assessed. In Experiment 2, separate sets of rats of each strain were examined for locomotor responses (distance traveled and center time) under novelty conditions. Results show that F344 rats self-administer more cocaine than Lewis or Sprague-Dawley rats under both schedules and emit more ineffective lever presses--a possible measure of craving. Strain comparisons of locomotor responses suggest that center time, not activity, relates to self-administration behavior. Maintenance studies of cocaine self-administration rather than acquisition may better reflect vulnerability to addiction.
作者先前证明，Fischer 344（F344）和Lewis近交系大鼠在可卡因自我给药的习得方面存在差异。其他研究表明，在远交Sprague-Dawley大鼠中，新环境中的运动活动可预测药物自我给药的习得和维持。本研究旨在确定这种关系是否也适用于F344和Lewis大鼠。在实验1中，对F344、Lewis和Sprague-Dawley大鼠进行可卡因自我给药训练，并在固定比率和累进比率强化程序下用几种剂量进行测试。评估自我给药的输注以及无效的主动杠杆按压——即在输注和暂停期间发出的按压。在实验2中，检查每组各品系大鼠在新奇条件下的运动反应（行进距离和中央时间）。结果表明，在两种程序下，F344大鼠比Lewis或Sprague-Dawley大鼠自我给药的可卡因更多，并且发出更多无效的杠杆按压——这可能是渴望的一种衡量指标。运动反应的品系比较表明，中央时间而非活动与自我给药行为有关。可卡因自我给药的维持研究而非习得研究可能更能反映成瘾易感性。
