Relationship between brain mitochondrial hexokinase and neuronal function: comparable effects of 2-deoxy-D-glucose and thiopental.
Mitochondrially bound brain hexokinase is solubilized by anesthetics and this effect has been suggested to contribute to anesthesia. In the present investigation the influence of the metabolic inhibitor 2-deoxy-D-glucose (2-DOG) was studied. An isolated rat brain preparation was used to avoid the contribution of peripheral reactions. Isolated rat brains were perfused for 45 min with media containing 4 mmol/l glucose, 10 mmol/l 2-DOG and/or 0.4 mmol/l thiopental. The EEG was monitored and acetylcholine, 2-DOG and its 6-phosphate, as well as the intracellular distribution of hexokinase activity were determined in brain tissue. Soluble hexokinase activity in brain cortex was enhanced by 2-DOG, as also by thiopental, and even more pronounced by both drugs used together, Results from in vitro experiments suggest that solubilization of mitochondrial hexokinase after 2-DOG is mediated by intracellularly accumulated 2-DOG-6-phosphate. 2-DOG produced a significant impairment of neuronal activity, revealing EEG patterns similar to those caused by thiopental anesthesia. Cortical acetylcholine levels were elevated by 2-DOG, as well as by thiopental, and again both drugs showed an additive effect when used in combination. This effect which may be the result of an inhibition of acetylcholine release, was also detectable in mice in vivo after 5 g 2-DOG/kg i.p., whereas the same dose of 3-O-methylglucose had no effect. The results provide further evidence that mitochondrial hexokinase may be involved in the relationship between cerebral metabolism and brain function.