Inhibition of [3H]spiroperidol binding by in vitro addition of ethanol

The in vitro addition of ethanol at concentrations greater than 0.2% produced an inhibition of [3H]spiroperidol binding. This inhibition was competitive, lowering the affinity without altering the maximum number of sites. Both the rates of association and dissociation were altered such that the ligand spent less time attached to the receptor. Since the binding was competitive, little inhibition was seen at ligand concentrations greater than 300 pM. These results are important for in vitro studies when drugs are dissolved in ethanol, and also for in vivo studies on the effects of ethanol.