Studies of dioxole ring substituted 3,4-methylenedioxyamphetamine (MDA) analogues

The 3,4-ethylidenedioxy and 3,4-isopropylidenedioxy analogues, EDA and IDA, respectively, of 3, 4-methylenedioxyamphetamine (MDA) were compared to MDA in drug-stimulated [3H]-serotonin overflow from prelabelled rat hippocampal slices, [3H]-dopamine overflow from prelabelled rat caudate slices, in their ability to displace the 5-HT2 agonist R-[125I]-DOI from rat brain cortical binding sites. They were also compared in the two-lever drug discrimination assay in rats, utilizing d-LSD tartrate (0.08 mg/kg) or MDMA.HCl (1.75 mg/kg) as the training stimulus. MDA and EDA were nearly equipotent in inducing release of both [3H]-monoamine transmitters, while IDA was considerably less potent. Pretreatment of hippocampal slices with the 5-HT-uptake inhibitor fluoxetine (3.2 microM) blocked the [3H]-5-HT overflow induced by MDA. In the drug discrimination experiments, complete substitution occurred with all three drugs in both LSD- and MDMA-trained rats. The ED50 values indicated that MDA had about twice the potency of EDA, and five times the potency of IDA in MDMA-trained rats. In the LSD-trained animals, MDA was about three times more potent than EDA and about seven times more potent than IDA. The KI values for displacement of R-[125I]-DOI generally parallel the results of the LSD transfer tests.