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Weinstein H, Johnson CL, Green JP. 
“Molecular Determinants For The Action Of Tryptamines On An LSD Receptor”. 
Fed. Proc.. 1977;36(3):290.
Actions of tryptamines were measured on: l)contraction of the rat stomach fundus, and 2)high-affinity binding of LSD by rat brain membranes. Potencies of tryptamines in contracting the stomach correlated (r=0.94) with potencies in inhibiting D-LSD binding, suggesting similar receptors. A direct relationship is found between biological potency and molecular reactivity characteristics: electron charge distributions, electrostatic potential fields around the molecules force vectors for optimal drug-receptor orientation; the localization of molecular sites most susceptible to polarization in drug-receptor complexes. QSAR studies on tryptamines show both potency on the fundus and the inhibition of LSD binding to be correlated with frontier electron densities at specific atoms (reflecting interaction with receptors by localized electron donation). New active structures and potencies of untested tryptamines were predicted and confirmed. The basis for the correlations is explained from quantum mechanical calculations: the frontier density dependence of potency follows the localization of the electron density ln the highest occupied molecular orbital (HOMO) of serotonin. the change in pharmacological potency with indole ring substitution comes from different HOMO density distributions (i.e. changes in localized polarizability) and different orientatlons of the interaction vectors, Ab-initio calculations of tryptamines and interactions with model receptor sites indicate mechanisms of action.
Notes # : Abstr. No. 111
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