REMOVAL OF HYDROXYL RADICAL FACILITATES CA2-DEPENDENT [H-3]GABA RELEASE BY PEROXYNITRITE()

We investigated mechanisms for enhancement of peroxynitrite (OONO-; 5 mu M)-evoked [H-3] gamma-aminobutyric acid (GABA) release. Hydroxyl ra dical scavengers such as N,N '-dimethylthiourea (DMTU), mannitol, and uric acid, significantly increased OONO--evoked [H-3]GABA release, whe reas urea showed no effects on the release. Removal of Ca2+ from incub ation buffer abolished the enhancement of the release by DMTU, althoug h DMTU showed no effects on the basal release with and without Ca2+ in extracellular space. These results indicate that hydroxyl radical sca vengers facilitate OONO--evoked [H-3]GABA release dependent on Ca2+. ( C) 1998 Elsevier Science B.V. All rights reserved.