CELL-PERMEANT CA2-VITRO AND IN-VIVO( CHELATORS REDUCE EARLY EXCITOTOXIC AND ISCHEMIC NEURONAL INJURY IN)

We report the characterization of the first successful treatment of ne uronal ischemic injury in vivo by cell-permeant Ca2+ chelators. The ch elators attenuated glutamate-induced intracellular Ca2+ increases and neurotoxicity in neuronal explant cultures. When infused intravenously in rats, permeant fluorescent BAPTA analogs accumulated in neurons in several brain regions. BAPTA-AM, infused in vivo, reduced Ca2+-depend ent spike frequency adaptation and post-spike train hyperpolarizations in CA1 neurons taken from treated animals. This effect was reproduced by direct injections of BAPTA into untreated neurons. The effects of three different chelators (BAPTA, 5,5'-difluoro BAPTA, and 4,4'-difluo ro BAPTA) on Ca2+-dependent membrane excitability varied with their Ca 2+ affinity. When the chelators' permeant forms were used to treat rat s prior to the induction of focal cortical ischemia, they were highly neuroprotective, as gauged by significant reductions in cortical infar ction volumes and neuronal sparing. The chelators' protective effects in vivo also reflected their affinity for Ca2+. This report provides t he most direct evidence to date that intracellular Ca2+ excess trigger s early neurodegeneration in vivo and contributes a novel therapeutic approach to neuronal ischemia of potential clinical utility.