Lithium effects on rat brain glucose metabolism in vivo. Effects after administration of lithium by various routes.

The effects of lithium on several brain energy metabolites were investigated in rats. Lithium was administered by three alternative routes: 1) in food, 2) via IP injection, or 3) intracisternally via the suboccipital route. Lithium given in food induced permanent changes, mainly in glycolytic processes and in glycogen content. Lithium injected IP induced, in addition, several changes which depended on the increase in brain lithium concentration following injection of lithium. These changes in brain metabolites disappeared as brain lithium concentration stabilized. Intracisternal injection of lithium produced brain lithium concentrations between 1 and 2 mmoles/kg wet wt., with a mean of about 1.6 mmoles/kg wet wt. Lithium concentrations below about 1.6 mmoles/kg wet wt. induced changes in brain metabolites which were similar to the changes seen after IP injection of lithium. Lithium concentrations above about 1.6 mmoles/kg wet wt. induced changes in several brain metabolites which were at variance with the changes induced by lower lithium concentrations. These changes were in many respects similar to changes in brain metabolites seen in rats exposed to convulsive treatment. It is hypothesized that such metabolic changes during lithium treatment, in discrete areas of the brain with higher concentration of lithium, e.g., hypothalamus, might be related to the prophylactic effect of lithium treatment in man.