Differential effects of some transition metal cations on the binding of beta-carboline-3-carboxylate and diazepam.

The interaction of benzodiazepines and beta-carbolines with metal cations was investigated. Among numerous transition metal cations, only three, CO2+, Ni2+ and Zn2+, specifically inhibited the binding of [3H]beta-carboline-3-carboxylate ethyl ester (beta-CCE). The effects of these cations on [3H]beta-CCE binding were exactly opposite to those on [3H]diazepam binding. The effects of these cations was not dependent on lipid peroxidation. The differential effect of these cations may reflect a general difference in the way agonists and antagonists bind to the benzodiazepine receptor.