Rate-dependent Effects of drugs. II. effects of some major tranquilizers on multiple fixed-ratio, fixed-interval schedule performance

Abstract

The effects of promazine, chlorpromazine, triflupromazine, prochlorperazine, trifluoperazine, perphenazine, fluphenazine, haloperidol, benzquinamide, tetrabenazine and chlorprothixene were determined on the rate of conditioned key pecking of pigeons under a multiple fixed-ratio 30, fixed-interval 5-minute schedule of food presentation. Chlorpromazine, prochlorperazine, perphenazine, chlorprothixene and tetrabenazine decreased responding relatively more within the fixed-interval component than within the fixed-ratio component and also produced rate-dependent effects within the fixed interval component, increasing the low rates of responding early in the fixed-interval but decreasing the high rates of responding in the terminal parts of the fixed interval. Triflupromazine, trifluoperazine, fluphenazine and haloperidol also decreased responding relatively more within the fixed-interval component than within the fixed-ratio component, but did not produce rate-dependent effects within the fixed-interval component. Both low and high rates of responding within the fixed interval were decreased only by these four drugs and they produced small and inconsistent decreases in the quarter-life values. Promazine and benzquinamide decreased responding relatively more within the fixed-ratio component than within the fixed-interval component and also produced rate-dependent effects within the fixed-interval component. There was a structure-activity relationship between the chemical group on the benzene ring of the phenothiazine nucleus and the rate-dependent effect on responding within the fixed-interval component. Phenothiazines with a hydrogen or chlorine group on the benzene ring produced a rate-dependent effect on responding within the fixed interval, while phenothiazines with a trifluoromethyl group on the benzene ring did not produce a rate-dependent effect on responding within the fixed interval.