INITIAL CHARACTERIZATION OF PMMA AS A DISCRIMINATIVE STIMULUS

The phenylisopropylamine PMMA or N-methyl-1-(4-methoxyphenyl)-2-aminop ropane, a structural hybrid of paramethoxyamphetamine (PMA) and metham phetamine, has been previously shown to unexpectedly lack amphetamine- like or hallucinogen-like stimulus properties in animals. For example, in tests of stimulus generalization, neither a (+)amphetamine stimulu s nor a DOM stimulus generalized to PMMA. It has also been shown, howe ver, that stimulus generalization does occur in animals trained to dis criminate the designer drug MDMA (''Ecstasy'' or ethyl-1-(3,4-methylen edioxyphenyl)-2-aminopropane) from vehicle. In order to further charac terize this unique agent, we trained a group of six Sprague-Dawley rat s to discriminate 1.25 mg/kg of PMMA (ED50 = 0.44 mg/kg) from saline v ehicle. The PMMA stimulus failed to generalize to the phenylisopropyla mine stimulant (+)amphetamine, or to the phenylisopropylamine hallucin ogen DOM. Stimulus generalization occurred to (+)MDMA (ED50 = 1.32 mg/ kg) and S(+)MDMA (ED50 = 0.48 mg/kg). Partial generalization occurred with R(-)MDMA, PMA, 3,4-DMA, and fenfluramine. The PMMA stimulus also generalized to the alpha-ethyl homolog of PMMA (EH/PMMA, ED50 = 1.29 m g/kg). Taken together, the results of these studies suggest that PMMA is an MDMA-like agent that lacks the amphetamine-like stimulant charac ter of MDMA. These findings support our previous suggestion that PMMA be considered the structural parent of the MDMA-like family of designe r drugs. (C) 1997 Elsevier Science Inc.