Screening of Thiol Compounds: Depolarization‐Induced Release of Glutathione and Cysteine from Rat Brain Slices

Superfusates from rat brain slices were screened for thiol compounds after derivatization with monobromo‐bimane by reversed‐phase HPLC. Only glutathione and cysteine were detected. The Ca2+‐dependent release of these compounds from slices of different regions of rat brain was investigated, applying a highly sensitive and reproducible quantification method, based on reduction of superfusates with dithiothreitol, reaction of thiols with iodoacetic acid, precolumn derivatization with o‐phthalaldehyde reagent solution, and analysis with reversed‐phase HPLC. This methodology allowed determination of reduced and total thiols in aliquots of the same superfusates. Mostly reduced glutathione and cysteine were released upon K+ depolarization and the Ca2+ dependency suggests that they originate from a neuronal compartment. The GSH release was most prominent in the mesodiencephalon, cortex, hippocampus, and striatum and lowest in the pons‐medulla and cerebellum. This underscores a physiologically significant role for glutathione in CNS neurotransmission.