INTERACTIONS BETWEEN ANESTHETICS AND LIPID MIXTURES - NORMAL ALCOHOLS

The effects of normal alcohols up to 1-dodecanol on phase transitions in phosphatidylcholines and phosphatidylethanolamines were studied using chlorophyll a as fluorescent probe. With the phosphatidylcholines, alcohols up to octanol cause a lowering of the transition temperature and a broadening of the transition, whereas for dipalmitoylphosphatidylethanolamine, only a lowering of the transition is observed. The lowering of the phase transition temperature in dipalmitoylphosphatidylcholine by butanol and hexanol is close to that expected for ideal behavior, but the behavior of the longer chain alcohols becomes less ideal. The effects of these alcohols on mixtures of lipids were studied, and they illustrate the care necessary if these plots of temperatures of onset and completion of gel phase formation are to be called phase diagrams. The effect of 1-octanol on mixtures of lipids is to increase the proportion of lipid present in the liquid-crystalline state. 1-Decanol increases the phase transition temperature for dimyristoylphosphatidylcholine and lowers the transition temperature for dipalmitoylphosphatidylcholine; 1-dodecanol raises the transition temperature for both phosphatidylcholines, but it lowers that for dipalmitoylphosphatidylethanolamine. Dodecanol appears to behave in these lipid bilayer membranes as a lipid with a phase transition temperature of approximately 55.degree. C. Anesthesia is discussed as a phenomenon of liquidus extension: alcohols up to 1-octanol increase the proportion of lipid in the liquidus state and result in anesthesia, whereas the longer alcohols do not, and result in catalepsy.