ETHANOL AND GLUTATHIONE ON NMDA RECEPTOR FUNCTION

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The NMDA-stimulated glutamate receptor Subtype in the brain appears to be involved in many important neuronal processes such as neuronal development, neuronal toxicity and learning and memory. Studies in our and other laboratories have shown that NMDA-receptor mediated processes in the brain are highly sensitive to inhibition by ethanol. Recent work in my laboratories has shown that glutathione (gamma-glutamylcysteinylglycine) stimulates NMDA receptors in an apparent competitive manner to enhance calcium entry through NMDA-stimulated ion channels. Glutathione is found in high concentrations in the brain, particularly high in glial cells. Recent work has shown that glutathione is released from glial cells in a robust manner. Taken together with recent results from my laboratories, the evidence suggests that glutathione (released from glial cells) may activate and possibly regulate NMDA receptor function. The overall objective of the proposed research will be to characterize the interactions of glutathione on NMDA receptor function and to determine the influence of acute and chronic alcohol exposure and prenatal ethanol exposure on the synthesis and release of glutathione and to study the influence of acute and chronic ethanol and prenatal ethanol exposure on glutathione interactions with NMDA receptors. Initially, studies will be conducted to characterize the effects of acute and chronic ethanol and fetal ethanol exposure on the brain concentrations and turnover of reduced (GSH) and oxidized (GSSG) glutathione. Brain regions to be studied will be those with high (cerebellum, cerebral cortex, hippocampus), intermediate (striatum) and low (pons-medulla) densities of NMDA-receptors. Studies are also designed to determine the effects of ethanol on the interactions of glutathione (GSH and GSSG) added in vitro on calcium entry through NMDA-stimulated channels in dissociated neurons. Experiments will also be carried out to demonstrate the mechanistic effects of ethanol in which receptor binding studies will be conducted on membranes from newborn and adult brain regions. The effects of invitro ethanol (5 - 100 mM) and chronic ethanol and its interactions with glutathione will be Studied. Experiments will be conducted on the effects of ethanol and glutathione on the Kd and Bmax for 3H-CPP (NMDA competitive site), 3H-glycine (co-agonist site), and H-MK-801 (allosteric, channel inhibitory PCP site) binding. Finally, studies are designed to characterize the effects of chronic ethanol administration to pregnant, female rats on the glutathione/NMDA-receptor interactions in dissociated neurons from newborn rat pups. These studies will address the question of the possible role that glutamate containing peptides may play in fetal abnormalities after maternal ethanol exposure.