GM1 GANGLIOSIDE REDUCES GLUTAMATE TOXICITY TO CORTICAL-CELLS - LOWERED LDH RELEASE AND PRESERVED MEMBRANE INTEGRITY

As an in vitro model of CNS excitatory amino acid (EAA) injury, rat co rtical neuronal cultures were challenged with glutamate (0.5 or 10 mM) and the levels of released lactate dehydrogenase (LDH) were monitored at 1 h, 1, 2, and 7 d. LDH release is correlated with levels of plasm a membrane damage. GM1 has been shown to be continuously distributed o n the outer surface of CNS cellular membranes. By staining for the dis tribution of endogenous GM1 ganglioside using cholera toxin/antitoxin immunohistochemistry, we were able to assess morphologically cellular plasma membrane integrity after damage. We used these two measures (LD H and GM1 localization) to study the neuroprotective effects of exogen ous GM1 ganglioside to further elucidate its mechanism. Cortical cultu res derived from 15-d rat fetuses were subjected to the glutamate chal lenge for 30 min. Parallel cultures were either pre- or posttreated wi th 80 muM of GM1. Exposure to 10 mM glutamate caused a highly signific ant increase in LDH release at 1-48 h. Pretreatment with GM1 reduced t he release, whereas post-treatment reduced the LDH release even more. Plasma membrane changes observed by the GM1 immunohistochemistry refle cted the LDH release data. All cultures treated with GM1 evidenced sub stantial structural integrity (continuous staining of GM1 along peryka rya and processes) as com red to untreated cultures. These data suppor t our hypothesis that GM1 treatment (pre- and post-) reduces plasma me mbrane damage.