Interactions of beta-carbolines with the benzodiazepine receptor: structure-activity relationships

The effects of a number of beta-carboline derivatives on [3H]flunitrazepam binding to the benzodiazepine binding site were investigated. The potency of beta-carbolines at the benzodiazepine binding site appeared to be determined largely by the aromaticity of the molecule. Norharmane-3-carboxylic acid ethyl ester was considerably more potent (IC50 10 nM) than its tetrahydro-beta-carboline analogue (IC50 6 microM). There is essentially no difference in potency between the (+)- and (--)-forms of the tetrahydro-beta-carboline-3-carboxylate analogues.