Enhancement of the behavioral effects of 2,5-dimethoxy-4-methyl-amphetamine (DOM) by pretreatment with p-chlorophenylalanine.

Seven food deprived male rats were trained to press a bar on a fixed ratio-40 (FR-40) schedule of food reinforcement. Administration of 0.5 mg/kg 2,5-dimethoxy-4-methyl amphetamine (DOM) immediately before the start of the session resulted in cessation of responding for some portion of the 40-min test session. Three successive days of p-chlorophenylalanine (PCPA) administration (100 mg/kg) 30 min after each session reduced 5-hydroxytryptamine (5-HT) to 15-26% of control concentrations in various brain regions but did not alter control rates of responding under the FR-40 schedule. Administration of 0.5 mg/kg DOM following this PCPA pretreatment resulted in a greater amount of nonresponding than observed earlier. These data suggest that the effects of the phenethylamine hallucinogen DOM are enhanced by disruption of 5-HT neuronal activity.