Nader M A, Thompson T
Department of Psychology, University of Minnesota.
Pharmacol Biochem Behav. 1989 Mar;32(3):643-9. doi: 10.1016/0091-3057(89)90011-7.
Twelve pigeons were initially trained under either a fixed-ratio (FR) 50 or differential-reinforcement-of-low-rate (DRL) 10-sec schedule of food presentation. After 50 sessions of exposure to the foregoing schedules all pigeons key pecked under a fixed-interval (FI) 90-sec schedule. Key-peck rates differed as a function of schedule history, with FR-history subjects responding at significantly higher rates under the FI schedule than DRL-history subjects. To better compare methadone's rate-altering effects on baseline response rates, 8 naive pigeons were trained from the outset to key peck under an FI 90-sec schedule and were subsequently divided into 2 groups based on overall response rates (groups FI-H and FI-L). After at least 40 sessions under the FI schedule methadone dose-response curves were determined at doses of 0.6, 1.2 and 2.4 mg/kg. Low and intermediate methadone doses did not effect key-peck rates by pigeons with an FR history compared to significant rate decreases by pigeons having comparable rates but without a history of responding under an FR schedule (group FI-H). No differential effects following methadone were observed in low-rate subjects (DRL history and FI-L). When methadone (9.0 and 12.0 mg/kg/day) was administered chronically, response rates of all subjects were initially suppressed, with FI control subjects showing more complete recovery of drug-free baselines than either FR- or DRL-history groups. Naloxone (1.0 mg/kg) reversed methadone's rate-decreasing effects, although these actions were significantly less in subjects with prior experience under DRL schedules. Following completion of the chronic phase, and when subjects had been drug free for at least 14 sessions, the methadone dose-response curve was redetermined. The differential effects of methadone associated with reinforcement history were no longer evident, suggesting that a drug history can interact with a schedule history. These experiments add to the growing body of evidence indicating that prior experience can influence the behavioral actions of drugs independent of control rate of responding. Moreover, the data reveal that the influence of reinforcement schedule history depends on whether drugs are administered acutely or chronically.
12只鸽子最初接受固定比率（FR）50或低比率差别强化（DRL）10秒的食物呈现训练计划。在50次接触上述训练计划后，所有鸽子在固定间隔（FI）90秒的训练计划下进行啄键。啄键率因训练计划历史而异，有FR历史的鸽子在FI训练计划下的反应率显著高于有DRL历史的鸽子。为了更好地比较美沙酮对基线反应率的速率改变作用，8只未接受过训练的鸽子从一开始就在FI 90秒的训练计划下接受啄键训练，随后根据总体反应率分为两组（FI-H组和FI-L组）。在FI训练计划下至少进行40次训练后，测定美沙酮在0.6、1.2和2.4mg/kg剂量下的剂量反应曲线。与具有可比反应率但没有在FR训练计划下反应历史的鸽子（FI-H组）相比，低剂量和中等剂量的美沙酮对有FR历史的鸽子的啄键率没有影响，但有显著的速率下降。在低反应率的鸽子（DRL历史和FI-L组）中未观察到美沙酮的差异效应。当长期给予美沙酮（9.0和12.0mg/kg/天）时，所有受试者的反应率最初都受到抑制，FI对照组的无药基线恢复比FR或DRL历史组更完全。纳洛酮（1.0mg/kg）逆转了美沙酮的速率降低作用，尽管在有DRL训练计划经验的受试者中这些作用明显较小。在慢性期结束后，当受试者至少14次无药时，重新测定美沙酮剂量反应曲线。与强化历史相关的美沙酮差异效应不再明显，这表明药物历史可以与训练计划历史相互作用。这些实验增加了越来越多的证据，表明先前的经验可以独立于反应控制率影响药物的行为作用。此外，数据表明强化训练计划历史的影响取决于药物是急性还是慢性给药。
