Behavior of Rats Under Fixed Consecutive Number Schedules: Effects of Drugs of Abuse

Abstract

Four rats responded under a simple fixed consecutive number schedule in which eight or more consecutive responses on the run lever, followed by a single response on the reinforcement lever, produced the food reinforcer. Under this simple schedule, dose-response curves were determined for diazepam, morphine, pentobarbital, and phencyclidine. The rats were then trained to respond under a multiple fixed consecutive number schedule in which a discriminative stimulus signaled when the response requirement on the run lever had been completed in one of the two fixed consecutive number component schedules. Under control conditions, the percentage of reinforced runs under the multiple-schedule component with the discriminative stimulus added was much higher than the percentage of reinforced runs under the multiple-schedule component without the discriminative stimulus. All of the drugs decreased the percentage of reinforced runs under each of the fixed consecutive number schedules by increasing the conditional probability of short run lengths. This effect was most consistently produced by morphine. The drugs produced few differences in responding between the multiple fixed consecutive number components. Responding under the simple fixed consecutive number schedule, however, was affected at lower doses of the drugs than was responding under the same fixed consecutive number schedule when it was a component of the multiple schedule. This result may be due to the difference in schedule context or, perhaps, to the order of the experiments.

The pharmacology of impulsive behaviour in rats II: the effects of amphetamine, haloperidol, imipramine, chlordiazepoxide and other drugs on fixed consecutive number schedules (FCN 8 and FCN 32)

“…Picker et al (1987) examined the effects of opiate agonists and antagonists on FCN responding in rats and obtained reductions in accuracy with most, but not all, of these compounds. Recently, Snodgrass et al (1997) reported the effects of diazepam, pentobarbital, PCP and morphine on FCN 8 schedules, and concluded that "responding under the FCN schedule is not very useful in differentiating amongst drugs. Each of the drugs disrupted stimulus control and they all decreased the rate of responding..." (Snodgrass et al 1997, p. 130).…”