Discriminative stimulus properties of (+/-)-3,4-methylenedioxymethamphetamine and (+/-)-3,4-methylenedioxyamphetamine in pigeons.

Pigeons trained to discriminate (+)-amphetamine (AMPH) from saline in a two-key food-maintained drug discrimination paradigm, were used to investigate the discriminative stimulus (DS) effects of two structural analogues of amphetamine, namely (+/-)-3,4-methylenedioxymethamphetamine (MDMA) and (+/-)-3,4-methylenedioxyamphetamine (MDA). After discrimination performance was stable (90% injection-appropriate responding), test sessions with various doses of AMPH were conducted and a dose-dependent relationship for AMPH-appropriate responding was obtained. Both MDMA (3.0 mg/kg) and MDA (3.0 or 5.6 mg/kg) substituted for AMPH; however, at these doses MDA produced a greater decrease in response rate compared to AMPH and MDMA. Furthermore, while MDMA and MDA were similar in potency in producing drug-appropriate responding, both were less potent than AMPH. These results indicate that MDMA and MDA have DS effects similar to AMPH in pigeons.