Nucleoside map of the human central nervous system.

Nucleosides are neuromodulators that have a wide range of biological roles in the brain. In order to better understand the function of nucleosides in the human central nervous system (CNS), we constructed a nucleoside map showing the concentration of various nucleosides and their metabolites using post mortem samples from 61 human brain areas and 4 spinal cord areas. We evaluated in vivo tissue levels of four nucleosides (uridine, inosine, guanosine, and adenosine) and three of their metabolites (uracil, hypoxanthine, and xanthine). The concentrations of nucleosides were unevenly distributed across different brain regions, where the highest levels were found in the cerebral cortex and basal ganglia, whereas the lowest concentrations were located in the locus coeruleus, the zona incerta, the substantia nigra, and the inferior colliculus. The regional differences in nucleoside levels in the CNS may reflect the distinct physiological functions adopted by these compounds in different brain areas.