SYNAPTIC PLASMA-MEMBRANE STRUCTURE AND POLARITY OF LONG-SLEEP AND SHORT-SLEEP MICE

Membrane dielectric as a primary basis for effects of ethanol was exam ined in synaptic plasma membranes (SPM) of genetically selected ethano l-sensitive long-sleep (LS) and ethanol-resistant short-sleep (SS) mic e. Multifrequency phase and modulation fluorometry of diphenylhexatrie ne (DPH) was used to resolve structural and dielectric differences in the membrane interior core. Fluorescence spectral peak ratios, fluores cence lifetime analysis, and initial rates of photoreaction of DPH in SPM provided sensitive measures of SPM interior core dielectric proper ties. The membrane microenvironment sensed by DPH was more polar in SP M from SS mice than in SPM from LS mice. Physiological concentrations of ethanol in vitro (25-75 mM) increased the SPM interior core dielect ric and potentiated photoreaction of DPH with other membrane component s of SPM from LS, but not SS, mice. These effects of ethanol in vitro were maximal by 75 mM ethanol and/or exacerbated at higher ethanol. In addition, ethanol in vitro increased the fraction of DPH associated w ith photoreaction products with lipids from SPM of ethanol-sensitive L S mice. The data were consistent with ethanol in vitro increasing the polar molecules (ethanol and/or water) of SPM from LS but not SS mice. It is suggested that ethanol alters the polarity and increases reacti vity of the interior core lipid-protein interface. (C) 1994 Academic P ress, Inc.