Blood and brain ethanol concentrations during absorption and distribution in long-sleep and short-sleep mice

It is often assumed that blood ethanol content accurately reflects brain ethanol content. In previous studies we have found that at the time of regaining the righting response blood and brain ethanol levels were identical, and blood ethanol could be used to predict brain ethanol level. It is likely, however that shortly after the administration of ethanol, blood and brain ethanol levels would differ. For this study, venous blood (orbital sinus) and brain ethanol levels were measured in long-sleep and short-sleep mice within the first 30 min following ethanol administration (2.5-6.0 g/kg). Ethanol was administered intraperitoneally or intragastrically. For both lines of mice and for every dose, brain ethanol concentrations were significantly greater (as much as 100 mg/dl) than blood ethanol levels for the first 6 min, and peak blood and brain ethanol levels were reached 4 to 6 min after dosing. Approximately 6 to 10 minutes (depending on dose and line of mouse) was required for blood and brain concentrations to reach equilibrium. At the time of loss of the righting response, brain ethanol levels were significantly higher than blood ethanol levels. These results indicate that within the first 6 min after administration of ethanol, blood ethanol level is not suitable for the assessment of brain ethanol content.