All local anesthetics bind to the biomembrane by its nitrogen atom in the molecule

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The interaction between various local anesthetics and the phospholipid membrane was examined by ^1HNMR (Nuclear Magnetic Resonance) spectroscopy. In order to measure the extent of proximity of various local anesthetics to the membrane, We examinined the chemical shift value and broadening of half-width of choline methyl signal of the membrane. Electrostatic interaction was seen between positively charged nitrogen atom of local anesthetics and negatively charged oxygen atom of phospholipid membrane. It was also determined that binding ability to the membrane of tetracaine and dibucaine, both of which possess two positively charged nitrogen atoms, was stronger than that of anesthetics such as lidocaine, procaine and bupivacaine, possessing only one positively charged nitrogen atom. On the other hand, when the positively charged nitrogen atom is surrounded by bulky carbon chains, such as cocaine, the chemical shift and broadening of half-width of choline methyl signal in the membrane were virtually unaffected. The binding ability of local anesthetics to the phospholipid membrane was found to be directly proportional to the anesthetic potency, suggesting that positively charged nitrogen atom of local anesthetics plays an important role in the action mechanism of local anesthetics.
北海道医療大学の論文