Objective: Following acute administration, ethanol has been assumed to be evenly distributed throughout the brain. However, some evidence exists for unequal extracellular levels of ethanol in different areas of the brain, suggesting the existence of locally elevated intracellular levels. The aim of this study was to investigate the relative tissue levels and rates of decline of ethanol in various regions of the brain and in the plasma of rats.
Method: Adult male Wistar rats (250-300 g) were injected intraperitoneally with a 14% ethanol/water solution at a dose of 1 g/kg of body weight. Brain and plasma samples were analyzed by an enzymatic rate method 30, 60, 90, or 120 minutes after injection for ethanol content.
Results: The highest tissue and plasma concentrations of ethanol occurred 30 minutes after administration, with concentrations of ethanol being highest in the striatum. All regions of the brain and plasma followed zero-order kinetics of elimination of ethanol; however, the rate of elimination in the brain declined at a slower rate than in the plasma. The rate remained constant during the 90-minute period. Elimination was slower in the brain than in the plasma.
Conclusions: Ethanol can accumulate to higher levels and can be eliminated more slowly from the brain than from the plasma, thus raising questions about blood alcohol testing as a measure of intoxication. The higher level of ethanol in the striatum, an area implicated in movement regulation and substance addiction, thus may have a significant bearing on the neurological effects and addictive properties of ethanol.