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The effects of ethanol on physicochemical and enzymatic perturbations of neuronal membranes were examined. Using synaptic plasma membrane (SPM) isolated from cerebral cortex of Sprague-Dawley rats, a biphasic mode of action for ethanol was observed with (Na+ + K+)-ATPase, but not with Ca2+-ATPase or acetylcholinesterase. (Na+ + K+)-ATPase was found to be more sensitive to low concentration of sodium deoxycholate treatment than Ca2+-ATPase. A sharp transition break of (Na+ + K+)-ATPase activity in response to temperature changes was found with SPM preparation. Arrhenius plots of the response also indicated that (Na+ + K+)-ATPase is more sensitive to temperature changes than Ca2+-ATPase. The fluorescence polarization of TNS-membrane complex decreases as ethanol concentration increases, indicating an increase in membrane fluidity. However, ethanol, at low concentration (less than 0.3%) appears to elevate TNS fluorescence, but at higher concentration (3%) ethanol tends to lower the intensity of maximal emission. The results of this study indicate that ethanol may interact with the synaptic plasma membranes and elicit specific biochemical responses depending on the concentration of the alcohol used.

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The effect of aging on Ca2+ -transport in synaptosomal preparations from rat brains was assessed by measuring the accumulation of radioactive 45Ca within these particles. Four groups of rats at 6, 12 24 and 30 months of age were used for this study. Synaptosomal particles were isolated from the cerebral cortex of each animal and the radioactive 45Ca inside the particles were measured after incubating the particles with media containing an energy source and 45Ca Cl2. Results indicated that the transport of 45Ca was lower in the younger rats than the older groups. A 20% increase was consistent with the old rats (30 mo) as compared with the young ones (6 mo). The increase in Ca2+ -transport across synaptic plasma membranes may be related to the transmitter release and behavioral activity after senescence.

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