Pharmacologic profile of amphetamine derivatives at various brain recognition sites: selective effects on...

Ring-substituted psychoactive derivatives of amphetamine exhibited high affinities for a number of serotonin recognition sites. Derivatives of 2,5-DMA exhibited preferential high affinity at 5-HT2 serotonin receptors when compared to their relative affinities at 5-HT1 serotonin receptors. Furthermore, 2,5-DMA derivatives exhibited agonist-like binding characteristics at 5-HT2 serotonin receptors with the R(-) isomer being the more potent isomer. There were significant correlations between the in vitro affinities of 2,5-DMA derivatives at 5-HT2 serotonin receptors and their human hallucinogenic potencies as well as with their potencies in behavioral generalization studies, suggesting the importance of 5-HT2 serotonin receptors in mediating the hallucinogenic effects of the various 2,5-DMA derivatives. A pharmacological profile of the methylenedioxy-substituted amphetamine derivatives indicates that MDMA and MDA exhibited highest affinity for serotonin uptake sites, 5-HT2 serotonin, alpha 2-adrenergic and M-1 muscarinic receptors. The methylenedioxy amphetamine derivatives exhibited an inverse stereospecificity with respect to serotonin uptake sites versus postsynaptic 5-HT receptors with the S(+) isomer being more potent at the presynaptic recognition site, while the R(-) isomer was more potent at the postsynaptic recognition sites. Similar to the 2,5-DMA derivatives, MDMA and MDA exhibited agonist-like binding characteristics at 5-HT2 serotonin receptors. Unlike 2,5-DMA derivatives, MDMA and MDA demonstrated little selectivity for 5-HT2 versus 5-HT1 subtypes of receptors. The relatively weak hallucinogenic effects of the methylenedioxy-substituted amphetamine derivatives (when compared to the 2,5-DMA derivatives) may be mediated through actions at 5-HT2 serotonin receptors. In addition, the neurotoxic, psychotomimetic, analgesic, temperature regulation, and mood-altering effects of MDMA and other methylenedioxy-substituted derivatives may be mediated, in part, through their actions at other serotonin recognition sites in brain, including serotonin uptake sites and 5-HT1A serotonin receptors. Other behavioral, cardiovascular, and toxic effects of MDMA and related derivatives may be mediated by actions at other central and/or peripheral recognition sites, including muscarinic cholinergic receptors and alpha 2-adrenergic receptors, for which these compounds exhibit relatively high affinity. The precise mechanisms for the various effects of the amphetamine derivatives remain to be determined.