Department of Psychology, University of California, Santa Barbara, CA 93106-9660, USA.
Psychopharmacology (Berl). 2011 Apr;214(3):769-78. doi: 10.1007/s00213-010-2088-0. Epub 2010 Nov 18.
Evidence suggests that responsiveness to a drug-paired cue is predicted by the reinforcing magnitude of the drug during prior self-administration. It remains unclear, however, if this principle holds true when comparisons are made across drug reinforcers.
The current study was therefore devised to test the hypothesis that differences in the animals' responsiveness to a cocaine- or heroin-paired cue presented during extinction would reflect differences in the patterns of prior cocaine and heroin runway self-administration.
Rats ran a straight alley for single intravenous injections of either heroin (0.1 mg/kg/inj) or cocaine (1.0 mg/kg/inj) each paired with a distinct olfactory cue. Animals experienced 15 trials with each drug reinforcer in a counterbalanced manner. Start latencies, run times, and retreat behaviors (a form of approach-avoidance conflict) provided behavioral indices of the subjects' motivation to seek the reinforcer on each trial. Responsiveness to each drug-paired cue was assessed after 7, 14, or 21 days of non-reinforced extinction trials. Other animals underwent conditioned place preference (CPP) testing to ensure that the two drug reinforcers were capable of producing drug-cue associations.
While both drugs produced comparable CPPs, heroin served as a stronger incentive stimulus in the runway as evidenced by faster start and run times and fewer retreats. In contrast, cocaine- but not heroin-paired cues produced increases in drug-seeking behavior during subsequent extinction trials.
The subjects' responsiveness to drug-paired cues during extinction was not predicted by differences in the motivation to seek heroin versus cocaine during prior drug self-administration.
有证据表明，药物配对线索的反应性取决于先前自我给药期间药物的强化程度。然而，当在不同的药物强化物之间进行比较时，这一原则是否成立尚不清楚。
因此，本研究旨在检验以下假设：在消退期间呈现的可卡因或海洛因配对线索时，动物对药物线索的反应性差异反映了先前可卡因和海洛因跑道自我给药模式的差异。
老鼠在一条直的过道上奔跑，接受单次静脉注射，分别与独特的嗅觉线索配对，注射的药物是海洛因（0.1mg/kg/注射）或可卡因（1.0mg/kg/注射）。动物以平衡的方式经历了 15 次每种药物强化物的试验。开始潜伏期、运行时间和退缩行为（一种接近回避冲突的形式）提供了关于每个试验中动物寻求强化物的动机的行为指标。在 7、14 或 21 天的非强化消退试验后，评估对每种药物配对线索的反应性。其他动物接受了条件位置偏好（CPP）测试，以确保两种药物强化物能够产生药物线索关联。
虽然两种药物都产生了类似的 CPP，但海洛因在跑道上作为更强的激励刺激，表现为更快的开始和运行时间以及更少的退缩。相比之下，只有可卡因配对的线索而不是海洛因配对的线索在随后的消退试验中增加了药物寻求行为。
在消退期间，对药物配对线索的反应性不能通过先前药物自我给药期间对海洛因与可卡因的寻求动机的差异来预测。
