TY - JOUR T1 - Biphasic Effects of Halothane on Phospholipid and Synaptic Plasma Membranes: a Spin Label Study JF - Molecular Pharmacology JO - Mol Pharmacol SP - 879 LP - 882 VL - 11 IS - 6 AU - PER H. ROSENBERG AU - HANSJÖRG EIBL AU - ANTON STIER Y1 - 1975/11/01 UR - http://molpharm.aspetjournals.org/content/11/6/879.abstract N2 - Halothane at 0.16 and 0.32 mM increased, while at 9.3 mM it decreased, the order parameter in palmitoyllauroyllecithin vesicles containing stearic acid spin label I(12,3). A corresponding effect was seen in rat brain synaptic plasma membranes. In dipalmitoyllecithin vesicles the lateral diffusion of stearic acid spin label I(5,10) was inhibited by halothane at 0.32-1.60 mM and promoted by it at 9.3 mM. Halothane in these three membrane systems exerted a biphasic effect, low concentrations ordering and high concentrations disordering the lipid structure of the membranes. ACKNOWLEDGMENTS We thank Dr. W. Kühnle for the synthesis of androstane spin label. ER -