Local anesthetics and divalent cations have the same effect on the headgroups of phosphatidylcholine and phosphatidylethanolamine

The effects of the local anesthetic dibucaine on the membrane headgroup conformations of phosphatidylcholine and phosphatidylethanolamine were determined using ²H- and ³¹P-NMR. The size of the deuterium quadrupole splittings of the two methylene segments of the choline and ethanolamine groups changed dramatically and the 31-phosphorus chemical shift anisotropy of the phosphatidylcholine headgroup decreased by about 7 ppm in the presence of local anesthetic. The quadrupole splittings of the 3-glycerol and choline methyl segments were relatively insensitive to the addition of dibucaine. The headgroup data for dibucaine addition paralleled similar data for the addition of various cations. These NMR results agree with the previous observation that these drugs displace calcium from phospholipids. The effects of this local anesthetic on these headgroups were distinctly different from the changes induced by cholesterol, heat and the general anesthetic chloroform.