Cysteine sulfinic acid in the central nervous system: uptake and release of cysteine sulfinic acid by a rat brain preparation.

Uptake and release of cysteine sulfinic acid by synaptosomal fractions (P2) and slices of rat cerebral cortex were investigated. The P2 fraction had a Na+-dependent high-affinity uptake system for cysteine sulfinic acid (Km, 12 microM), which was restricted to the synaptosomes. High-affinity uptake of cysteine sulfinic acid was competitively inhibited by glutamate, aspartate, and cysteic acid. None of the various centrally acting drugs tested specifically inhibited this transport system. Release of [14C]cysteine sulfinic acid from preloaded cortical slices or P2 fractions was examined by a superfusion method, which avoided reuptake of released [14C]cysteine sulfinic acid. High K+ (56 mM) and veratridine (10 microM) stimulated the release of cysteine sulfinic acid from slices and the P2 fraction in a partly Ca2+-dependent manner. Diazepam at concentrations of 10 and 100 microM markedly inhibited the stimulated release, but not the spontaneous release, by cortisol slices. On the contrary, it had no effect on the stimulated release of cysteine sulfinic acid from the P2 fraction.