Changes in cortical synaptosomal plasma membrane fluidity and composition in ethanol-dependent rats.

Synaptosomal plasma membranes (SPM) were examined from the following four groups of rats: controls; rats acutely treated with single doses of ethanol; a prodromal-detoxication group (dependent-intoxicated); rats undergoing overt ethanol-withdrawal syndrome. Estimates of the apparent microviscosity of SPM over a range of temperatures indicated that temperature-induced changes in SPM fluidity were smaller during the prodromal detoxication phase. The cholesterol:phospholipid molar ratio significantly increased in SPM from the prodromal-phase rats, but to a lesser extent in rats undergoing ethanol withdrawal syndrome. The fatty acid content of SPM phospholipids was not significantly changed in any of the treatment groups. Addition of cholesterol in vitro to control membranes altered the apparent microviscosity similarly to the changes found in SPM of ethanol-dependent rats. These studies suggest that physical dependence upon ethanol may be related to changes in synaptosomal membrane composition and viscosity.