Weber K
Psychopharmacology (Berl). 1985;85(2):231-5. doi: 10.1007/BF00428421.
The purpose of this study was to test whether the effects of methylphenidate on rates of operant responding in hyperactive boys differed depending on the predrug baseline rates of responding. On the basis of the rate dependency hypothesis, dose-related decreases from high baseline rates and increases from low baseline rates would be predicted. A multiple FR-DRL (fixed ratio-differential reinforcement of low Rates) schedule was used to generate high and low rates of responding on a simple operant task, using nickels as reinforcers. Three dosage levels were used: placebo, 0.3 mg/kg, and 1.0 mg/kg of methylphenidate. Both experimenter and subject were blind to dosage level. Surprisingly, DRL response rates were not significantly affected by the drug, while FR rates increased linearly with increasing dose. Thus, the predicted between-schedule differences were not found. However, within the FR schedule, changes from baseline to postdrug rates within each active drug condition were consistent with the rate dependency hypothesis; i.e., subjects with lower baselines increased their response rates, while subjects with higher baselines decreased or did not change their rates. The opposite effect occurred following placebo.
本研究的目的是测试哌甲酯对多动男孩操作性反应率的影响是否因用药前的基线反应率不同而有所差异。基于速率依赖性假说，可以预测与剂量相关的高基线率下降和低基线率上升。采用多重固定比率-低速率差别强化（FR-DRL）程序，以镍币作为强化物，在一项简单的操作性任务中产生高反应率和低反应率。使用了三个剂量水平：安慰剂、0.3毫克/千克和1.0毫克/千克的哌甲酯。实验者和受试者均对剂量水平不知情。令人惊讶的是，DRL反应率并未受到药物的显著影响，而FR反应率则随剂量增加呈线性上升。因此，未发现预测的不同程序间差异。然而，在FR程序内，每种活性药物条件下从基线到用药后反应率的变化与速率依赖性假说一致；即基线较低的受试者提高了反应率，而基线较高的受试者降低了反应率或未改变反应率。安慰剂给药后则出现相反的效果。
