Journal of Neuroscience, Vol 8, 2164-2171, Copyright © 1988 by Society for Neuroscience
Zinc alters excitatory amino acid neurotoxicity on cortical neurons
JY Koh and DW Choi
Department of Neurology, Stanford University Medical Center, California 94305.
Recent studies have suggested that large amounts of free zinc may be
coreleased during excitatory synaptic transmission at glutamatergic
synapses, and may act postsynaptically to decrease actions mediated by
N-methyl-D-aspartate (NMDA) receptors, while often increasing
neuroexcitation mediated by quisqualate receptors. The present study
examined the ability of zinc to alter excitatory amino acid (EAA)
neurotoxicity. Murine cortical cell cultures were exposed to EAAs for 5 min
in defined solutions, and neuronal cell injury was examined the following
day both morphologically and by lactate dehydrogenase assay. Inclusion of
30-500 microM zinc in the exposure solution produced a zinc
concentration-dependent, noncompetitive attenuation of NMDA- induced
neuronal injury, with an ED50 of about 80 microM. In contrast, zinc
produced the same concentration-dependent potentiation of quisqualate
neurotoxicity; and with 500 microM zinc, a small potentiation of kainate
neurotoxicity was suggested. The effect of zinc on the neurotoxicity of the
broad-spectrum agonist glutamate was consistent with these effects on
specific agonists, as well as with a previous study showing that glutamate
neurotoxicity normally depends predominantly on NMDA-receptor activation.
Zinc produced a concentration-dependent reduction in glutamate-induced
neuronal injury in a fashion similar to that seen with NMDA, but less
effectively. In addition, despite this overall protective effect, zinc
paradoxically increased the glutamate-induced destruction of nicotinamide
adenine dinucleotide phosphate diaphorase (NADPH-d)-containing neurons, a
subpopulation that was shown in the preceding paper (Koh and Choi, 1988) to
exhibit resistance to NMDA receptor-mediated neurotoxicity, and
vulnerability to non-NMDA receptor-mediated neurotoxicity.(ABSTRACT
TRUNCATED AT 250 WORDS)