The family of drugs typified by MDMA produce their effects through multiple mechanisms of action in the body, and consequently produce three distinct cues which animals can be trained to respond to: a stimulant cue typified by drugs such as methamphetamine, a hallucinogen cue typified by drugs such as LSD and DOM,
and an "entactogen-like" cue which is produced by drugs such as MDAI and MBDB. These drugs cause drug-appropriate responses in animals trained to recognize the effects of MDMA, but do not produce responses in animals trained selectively to respond to stimulants or hallucinogens.
Because these compounds selectively release serotonin in the brain but have little effect on dopamine or noradrenaline levels, they can produce empathogenic effects but without any stimulant action, instead being somewhat sedating.
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http://en.wikipedia.org/wiki/MDAI#Effects