The membrane stabilizing activity of beta-adrenoceptor ligands. Quantitative evaluation of the interaction of phenoxypropanolamines with the [3H]batrachotoxinin A 20-alpha-benzoate binding site on voltage-sensitive sodium channels in rat brain.

The interaction of 12 phenoxypropanolamines, all ligands with high affinity towards beta-adrenoceptors, with the [3H]batrachotoxinin A 20-alpha-benzoate ([3H]BTX-B) binding site on voltage-sensitive sodium channels in a rat brain synaptosomal preparation, was studied as a measure for local anaesthetic activity. All derivatives are capable of displacing [3H]BTX-B from its specific binding site, penbutolol displaying the highest affinity. Multiple regression analyses were performed, correlating biological activity (pKi values) with physicochemical parameters. Lipophilicity is of prime importance in the established regression equations, but steric factors are relevant as well. Comparisons were made with analogous equations relating beta 1- and beta 2-adrenoceptor affinity with physicochemical parameters, leading to the conclusion that "cardioselective" beta-adrenoceptor ligands appear to have fewer membrane stabilizing properties.