NA-23 AND H-1-NMR STUDIES ON MELITTIN CHANNELS ACTIVATED BY TRICYCLIC TRANQUILIZERS

A dynamic Na-23 nuclear magnetic resonance (NMR) technique was applied to the exchange system of Na+ ions present inside and outside large unilamellar vesicles at an equivalent concentration. Addition of melittin to phosphatidylcholine vesicles did not induce any detectable Na+ transport across the membrane but subsequent addition of a trace of chlorpromazine or imipramine did induce Na+ transport. Because the formation of a drug-melittin adduct in a solution was detected by H-1 NMR, the activation of melittin channels was assumed to originate from the direct interaction of the drug and melittin.