Stafford D, LeSage M G, Glowa J R
Department of Pharmacology and Therapeutics, Louisiana State University Medical Center, Shreveport 71130-3932, USA.
Behav Pharmacol. 1999 Dec;10(8):775-84. doi: 10.1097/00008877-199912000-00009.
Previous reports indicate that intravenous pretreatment with phentermine can decrease cocaine-maintained responding without affecting food-reinforced responding under fixed-ratio schedules. The present experiments were designed to explore the generality of this effect using progressive-ratio schedules of reinforcement and different routes of phentermine administration. Unit doses of cocaine and food-pellet magnitudes were identified that maintained similar breaking points, and the effects of acute exposure to phentermine were assessed. In Experiment 1, a 'conventional' (one-trial) progressive-ratio schedule was used, in which response requirements increased after each reinforcer delivery; in Experiment 2, a 'modified' (five-trial) progressive-ratio schedule was used, in which response requirements increased after every five reinforcer deliveries. In one group of monkeys, responding was maintained by food; in another, cocaine infusions maintained responding. Phentermine (0.1-5.6mg/kg, intramuscularly (i.m.)) dose-dependently decreased breakpoints on both progressive-ratio schedules. There were no differences in phentermine's effects on cocaine- and food-maintained behavior. In Experiment 3, intravenous administration of phentermine had largely similar effects. Taken together with results from previous reports, these data suggest that the effects of phentermine pretreatment are influenced by the behavioral procedure used to maintain responding and/or by the efficacy of the food and cocaine reinforcers.
先前的报告表明，用苯丁胺进行静脉预处理可减少可卡因维持的反应，而在固定比率时间表下不影响食物强化的反应。本实验旨在使用累进比率强化时间表和不同的苯丁胺给药途径来探索这种效应的普遍性。确定了维持相似断点的可卡因单位剂量和食物颗粒量，并评估了急性接触苯丁胺的效果。在实验1中，使用了“传统”（单次试验）累进比率时间表，其中每次强化物递送后反应要求增加；在实验2中，使用了“改良”（五次试验）累进比率时间表，其中每五次强化物递送后反应要求增加。在一组猴子中，反应由食物维持；在另一组中，可卡因输注维持反应。苯丁胺（0.1 - 5.6mg/kg，肌肉注射（i.m.））在两种累进比率时间表上均剂量依赖性地降低了断点。苯丁胺对可卡因和食物维持行为的影响没有差异。在实验3中，静脉注射苯丁胺产生了大致相似的效果。结合先前报告的结果，这些数据表明苯丁胺预处理的效果受用于维持反应的行为程序和/或食物及可卡因强化物的效力影响。
