After prolonged treatment of rats with lithium (pellets, 0.21 lithium carbonate, or 0.5 mg/ml lithium chloride in drinking water) for three months, the level of lithium in plasma was 0.87 meq/liter; in several brain regions, between 1.06–1.39 μeq/g wet weight. The content of sodium and potassium in the plasma was normal. The level of potassium in the brain regions tested increased by 13–30 and that of sodium by about 10. Glycine levels increased significantly in all the regions (cerebral cortex, midbrain, cerebellum, and spinal cord). In the cerebellum GABA was also increased, while glutamine was decreased. In midbrain, apart from increases in glycine levels, alamine, valine, GABA and lysine were also increased. In the spinal cord, glutamic acid was also increased. Changes were largely in the putative neurotransmitters. Long-term treatment with lithium also influenced the high-affinity binding of 3Hspiperone in the cerebral cortex and corpus striatum. Two specific binding sites were found in both brain regions; the main change was the reduction in the lower affinity binding site (Bm
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