Temporal and regional differences in brain concentrations of lithium in rats.

Lithium (Li) concentrations have been estimated in several peripheral tissues (serum, heart, kidney, liver and skeletal muscle) and different brain areas (cortex, caudate nucleus, hypothalamus, diencephalon, midbrain, pons-medulla and cerebellum) at different intervals (0.5 to 48 h) after administrations of 3 mEq/kg of lithium chloride (LiCl). The Li concentrations in the brain areas increased gradually, reaching their peak at 8 h; the hypothalamus showed the highest concentration measured between 0.5 and 8 h; after 8 h the highest concentration was observed in the caudate nucleus, followed approximately by those of the cortex, rest of the diencephalon, and other areas. Concentration of Li in the skeletal muscle, although initially less, was maintained at a higher percentage of the initial level for more than 24 h compared to the other peripheral tissues.