The serotonin (5-HT) receptor affinities and behavioral (discriminative stimulus) properties of a series of 4-substituted derivatives of 1-(2,5-dimethoxyphenyl)-2-aminopropanes (2,5-DMA) were investigated. The substituents at the 4-position included H, OMe, OEt, Me, Et, F, Br, I, and NO2. Substituent lipophilicities (pi values) of these functionalities appear to have a minimal effect on either 5-HT receptor affinity or behavioral activity. Those derivatives previously found to be most potent in human studies possess significant affinity for 5-HT receptors. Furthermore, when rats trained to discriminate (+/-)-1-(2,5-dimethoxy-4-methylphenyl)-2-aminopropane (DOM) from saline were used, generalization was found to occur upon administration of the 4-substituted 2,5-DMA derivatives. Because a direct relationship exists between the ED50 values obtained from these discrimination studies and human hallucinogenic potencies, the discriminative stimulus paradigm, with DOM as a training drug, appears to be a useful tool for comparing the quantitative and qualitative (DOM-like) effects produced by certain hallucinogenic agents.

Serotonin receptor affinity and photelectron spectral data were obtained on a number of substituted N,N-dimethyltryptamines. Evidence is presented that electron-donating substituents in the 5-position lead to enhanced behavioral disruption activity and serotonin receptor affinity as compared to unsubstituted N,N-dimethyltryptamine and analogues substituted in the 4- or 6-position. Some correlation was found between ionization potentials and behavioral activity, which may have implications concerning the mechanism of receptor binding.