EFFECTS OF CHRONIC ETHANOL ADMINISTRATION ON NEURONAL MEMBRANE FLUIDITY IN VARIOUS REGIONS OF THE RAT-BRAIN

The neuronal membrane fluidity in six different regions of the rat bra in was measured by electron spin resonance spectrometry using the spin labels 5- and 16-doxylstearic acid (5- and 16-DS) after administratio n of ethanol solution (7%) for 3 weeks. The order parameter, calculate d from 5-DS spectra, which is utilized to assess the fluidity of the l ipid bilayer near the surface of the membrane, increased in the cerebr al cortex and hippocampus, and the motion parameter, calculated from 1 6-DS spectra, for the core of the lipid bilayer, increased in the cere bral cortex. On the other hand, almost no membrane fluidity change was observed in the striatum, midbrain, pons-medulla oblongata and cerebe llum. These results indicate that chronic ethanol administration does not decrease membrane fluidity evenly in all the regions of the brain.