Effects of response requirement upon human sedative self-administration and drug-seeking behavior.

Five male volunteers with histories of sedative drug abuse were given the opportunity to self-administer up to 20 oral doses per day of either diazepam (10 mg per dose) or sodium pentobarbital (30 mg per dose). Each dose was purchased with tokens earned by exercising on a stationary exercise bicycle. Each two minutes of exercise earned one token. In a mixed order across days the number of tokens required to purchase each dose was varied among 1, 3, 5, 8 and 10. Drug intake decreased as a function of increased response requirement for purchasing the drug. Response output for drug tended to be an inverted-U shaped function of the response requirement. Thus, the cost of drug doses act as a powerful environmental influence upon both of these aspects of drug abuse behavior - amount of drug consumed and amount of drug-seeking behavior.