Continuous monitoring of brain ethanol levels by intracerebral microdialysis

A method is described which allows simultaneous collection of blood and perfusate of discrete brain regions from an individual animal over several hours. This procedure involves catheterization of a peripheral blood vessel (jugular vein) and the insertion of a microdialysis probe into a specified brain area (lateral hypothalamus) for sampling of blood and brain perfusate, respectively. Using this procedure, levels of ethanol in blood and brain perfusates were determined by scintillation counting following administration of [¹⁴C]-ethanol (20 μCi) to adult male rats at a dose of 0.8 or 2.4 g/kg. Ethanol levels in brain and blood as well as the time-course of disappearance were dependent on the dose administered. Peak blood levels were observed in the first sample taken (i.e., at 10 min), whereas a slight delay was noted in the time to peak level in brain. At subsequent time points, a good correlation was observed between blood and brain perfusate radioactivity levels although perfusate levels were slightly lower. It is concluded that this approach will prove useful for investigating the molecular and cellular mechanisms of action of ethanol by enabling the direct correlation of blood and brain ethanol levels with various behavioral, electrophysiological and/or biochemical measures.