Effects of short-term lithium administration on tryptophan levels and 5-hydroxytryptamine synthesis in whole brain and brain regions in rats.

The effects of short-term lithium administration on tryptophan levels and 5-hydroxytryptamine (5-HT) synthesis in whole brain and brain regions in rats were studied. Short-term lithium administration was found to increase whole brain tryptophan levels without affecting whole brain 5-HT synthesis. However, the increase of tryptophan varied between various brain regions, which may possibly be due to differences in the synaptosomal uptake of tryptophan between brain regions. In the striatum, where the tryptophan increase was most pronounced, an increase in 5-HT synthesis was found too. These latter findings suggest that the increase in 5-HT synthesis might be due to an increase in tryptophan availability.