STRUCTURE AND POLARITY OF MOUSE-BRAIN SYNAPTIC PLASMA-MEMBRANE - EFFECTS OF ETHANOL IN-VITRO AND IN-VIVO

Structural and dielectric alteration by ethanol in vitro and chronic e thanol consumption were examined in synaptic plasma membranes (SPM) us ing diphenylhexatriene and charged diphenylhexatriene derivatives. The se fluorophores, in combination with multifrequency phase and modulati on fluorometry, allowed the examination of the surface and interior co re of SPM. Limiting anisotropy and rotational relaxation time demonstr ated that the synaptosomal plasma membrane surface domain was more rig id than the interior core domain. Ethanol in vitro fluidized the inter ior core and surface domains in SPM of the control, but not chronic et hanol-treated mice. Although the latter membranes were more rigid than control membranes, the intrinsic rigidity of the interior core of the synaptosomal plasma membrane did not strictly correlate with effects of ethanol in vitro. SPM of irradiated membranes were more rigid, but ethanol fluidized those membranes. Diphenylhexatriene lifetime and pho toreactivity were sensitive to the range of dielectric constants in th e SPM interior core. Ethanol in vitro increased both the surface and i nterior core range of dielectric constants of SPM from control but not chronic ethanol-treated animals. Thus, ethanol in vitro altered not o nly the fluidity but also the range of dielectric constants in both th e surface and interior core domains in SPM of control but not chronic ethanol-treated mice.