Comparison of behavioral properties of di- and tri-methoxyphenylisopropylamines

Prominent among the class of hallucinogenic phenylisopropylamines is the 2,5-dimethoxy substitution pattern; this pattern has long been recognized as being an important feature of the more potent agents within this class. The purpose of this present study was to explore the behavioral properties of a series of methoxylated phenylisopropylamines in order to determine the effect of other substitution patterns and the relative importance of individual methoxy groups. Rats, trained to discriminate the hallucinogenic agent 2,5-dimethoxy-4-methyl-phenylisopropylamine (DOM) from saline in a two-lever drug discrimination task, were challenged with a series of di- and trimethoxyphenylisopropylamines (i.e., DMA and TMA derivatives). DOM-stimulus generalization was found to occur with 2,4-DMA but not with 2,3-DMA, 2.6-DMA, or 3,5-DMA; generalization also occurred with 2,3,4-TMA, 2,3,5-TMA, 2,4,6-TMA and 3,4,5-TMA. The 2,4-dimethoxy pattern also emerges as an important feature among the more active agents.