Sc. Gilman et al., FREE-RADICALS ENHANCE BASAL RELEASE OF D-[H-3]ASPARTATE FROM CEREBRALCORTICAL SYNAPTOSOMES, Journal of neurochemistry, 62(5), 1994, pp. 1757-1763
Excessive generation of free radicals has been implicated in several p
athological conditions. We demonstrated previously that peroxide-gener
ated free radicals decrease calcium-dependent high K+-evoked L-[H-3]gl
utamate release from synaptosomes while increasing calcium-independent
basal release. The present study evaluates the nonvesicular release o
f excitatory amino acid neurotransmitters, using D-[H-3]aspartate as a
n exogenous label of the cytoplasmic pool of L-glutamate and L-asparta
te. Isolated presynaptic nerve terminals from the guinea pig cerebral
cortex were used to examine the actions and interactions of peroxide,
iron, and desferrioxamine. Pretreatment with peroxide, iron alone, or
peroxide with iron significantly increased the calcium-independent bas
al release of D-[H-3]aspartate. Pretreatment with desferrioxamine had
little effect on its own but significantly limited the enhancement by
peroxide. High K+-evoked release in the presence of Ca2+ was enhanced
by peroxide but not by iron. These data suggest that peroxide increase
s nonvesicular basal release of excitatory amino acids through Fenton-
generated hydroxyl radicals. This release could cause accumulation of
extracellular excitatory amino acids and contribute to the excitotoxic
ity associated with some pathologies.