Interaction of local anaesthetics with model phospholipid membranes. The effect of pH and phospholipid composition studied by quenching of an intramembrane fluorescent probe.

The interaction of local anaesthetics, tetracaine and procaine, with model phospholipid membranes has been examined by measurement of drug-induced quenching of the fluorescence of a membrane incorporated probe, 12-(9-anthroyl)stearic acid. The pH dependence of quenching curves obtained for neutral phosphatidylcholine and acidic phosphatidylserine bilayers indicates that, contrary to previous suggestions, both charged and uncharged forms of amine local anaesthetics may be incorporated into lipid membranes.