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The effect of various alkanols on the central nervous system was studied by using rat brain synaptosomal membranes as an in vitro model. The activity of (Ca2+/Mg2+)ATPase and the membrane fluidity were determined. The n-alkanols exhibited an increased molar inhibition of the ATPase activity with an increase in the carbon chain length up to 1-octanol. 1-octanol and 1-decanol caused a biphasic effect on the ATPase activity depending on the alkanol concentration, whereas 1-dodecanol caused a stimulation of the ATPase activity. All alkanols studied caused an increased fluidity of the membrane. Our results indicate that the effect of alkanols on the ATPase activity depends on changes in the border layer between the membrane and the surrounding medium and on a binding of the alkanols to the enzyme molecule. Furthermore, the two-way effect of 1-octanol and 1-decanol and the stimulatory effect of 1-dodecanol indicate that more mechanisms are involved. In addition, the results indicate that changes in the membrane fluidity do not seem to be a prerequisite of the ATPase inhibition.

The effect of toluene on the central nerve system was studied by using rat brain synaptosomal membranes as in vitro and in vivo models. The activity of Ca2+/Mg2+ ATPase and the membrane fluidity were determined. Short-term exposure in vivo to 500 p.p.m. of toluene had an inhibitory effect on the enzyme studied whereas long-term exposure to toluene caused an increased activity. Exposure to toluene had no effect at all on the membrane fluidity. The in vitro experiment showed an effect of toluene on both parameters. The alteration in the enzyme activity and membrane fluidity was parallel in the exposed animals as well as those of control. Our results show that long-term exposure to toluene affects nerve cell membranes by other mechanisms than those observed under in vitro conditions.

The effect of various solvents on the central nervous system was studied by using rat brain synaptosomal membranes as an in vitro model. The activity of (Ca2+/Mg2+) ATPase and the membrane fluidity was determined. The alteration of the ATPase activity depended on the physio-chemical characteristics of the solvent in question. Incubation with aliphatic alkanes caused a stimulation of the ATPase activity whereas mixed hydrocarbons as kerosene, white spirit and gasoline inhibited the enzyme. Incubation with chlorinated hydrocarbons caused a biphasic response dependent on the concentration. Oxygen-containing hydrocarbons exhibited various effects as found after incubation with hydrocarbons. The different effects of the solvents on the ATPase activity suggest that the lipophilicity of the solvents is one of more parameters affecting the membrane. Furthermore, the biphasic response following the incubation with chlorinated hydrocarbons indicates that more mechanisms are involved in the enzyme effect. The membrane fluidity is increased with higher concentrations of the solvents. From the results it is concluded that the ATPase activity depends not only on the membrane fluidity and volume, but also on the hydrophilic vicinity of the enzyme molecule.

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