Abstract
The influence of lithium administration on brain serotonin metabolism and the serum tryptophan level in rats was investigated. The brain tryptophan, serotonin and 5-hydroxyindole acetic acid contents did not change after a single injection of lithium, but did increase significantly after repeated injections. A single injection of lithium caused a marked decrease in the serum total tryptophan level, but did not change the ratio of free to albumin bound tryptophan. On the contrary, repeated injections of lithium caused a significant increase in serum total tryptophan, and decrease in the ratio of free to bound tryptophan. Addition of lithium ion to normal rat serum in vitro did not change the ratio of free to bound tryptophan. A single injection of lithium produced a marked rise in serum nonesterified fatty acid, which is known to affect the binding of tryptophan by albumin.
