Effect of L-DOPA on glucose oxidation and incorporation into glycogen in discrete brain regions of the rat.

Previous reports in which the [14C]deoxyglucose mapping technique was used, have demonstrated that systemic administration of L-DOPA can either increase or decrease glucose utilization in various brain regions. However, in the striatum, which contains a high concentration of dopamine, no conclusive results were found using this technique. In the present study we attempted, by implicating a different technique, to evaluate the effect of L-DOPA on glucose metabolism in the striatum. This approach is based on in vitro measuring of glucose oxidation to CO2 and its incorporation to glycogen. Rats were injected with carbidopa (100 mg/kg) and 1 h later with L-DOPA (50 mg/kg). The rats were sacrificed by decapitation 1 h after L-DOPA injection and the following brain regions were assayed for glucose oxidation to CO2 and its incorporation to glycogen: striatum, hypothalamus, hippocampus and prefrontal cortex. A significant increase of glucose oxidation of 50% was found in the striatum and hippocampus, while no change was demonstrated in the hypothalamus and cortex. The incorporation of glucose to glycogen was markedly reduced in the striatum and hippocampus while no change was found in the hypothalamus or cortex. The present results demonstrate that L-DOPA treatment increases glucose metabolism in specific brain areas. The mechanism involved might be an increase in cellular uptake of glucose and/or activation of enzymes participating in glucose metabolic pathways.