The antagonistic effect of an inhalation anesthetic and high pressure on the phase diagram of mixed dipalmitoyl-dimyristoylphosphatidylcholine bilayers.

Several workers have shown that phase transition-related changes in membrane lipids have a profound effect on membrane-solvated protein function. This phase transition temperature dependence has been explained as resulting from the formation of lateral phase separations within the membrane bilayer. The present study demonstrates that a clinical concentration of an inhalation anesthetic produces changes in both the phase transition temperature of pure lipid bilayers and the lateral phase separation temperature of mixed dipalmitoyl- and dimyristoylphosphatidylcholine bilayers of a magnitude sufficient to influence protein function. It is further shown that pressure is able to antagonize the effect of the anesthetic on these transition temperatures. It is proposed that anesthetic action within nerve membranes may be the result of changes in the lateral phase separation-controlled environment of the membrane-solvated proteins essential to nerve function.