The effect of psychostimulants on the reinforcing properties of drugs in pre- and postpubertal rats

Abstract

Chronic administration of psychostimulants produces a progressive augmentation in dopamine-mediated behaviors; a phenomenon known as behavior sensitization. Recent evidence suggests that in adult rats the appetitive properties of some drugs of abuse can be sensitized by the psychostimulant, amphetamine. The purpose of the present study was to further characterize the sensitizing effect of the psychostimulants on the appetitive properties of drugs of abuse. In the first experiment prepubertal rats were injected with amphetamine (0.5 mg/kg) 15 days prior to place conditioning with amphetamine (1.0 mg/kg). In the second experiment both pre- and postpubertal rats were injected with amphetamine (1.5 mg/kg), methylphenidate (2.0 mg/kg), or pemoline (10.0 mg/kg) 15 days prior to place conditioning with either amphetamine (1.5 mg/kg) or diazepam (1.0 mg/kg). Amphetamine-induced place conditioning was significantly greater in postpubertal subjects pretreated with amphetamine or pemoline when compared to prepubertal subjects receiving the same treatment. The psychostimulant pretreatments had no effect on spontaneous locomotion, amphetamine-induced locomotion, or conditioned locomotion.