In the mammalian retina, endogenous chelatable zinc was shown to be localised mainly in the photoreceptors and retinal pigment epithelium. Zinc localisation in the photoreceptors varied in light and dark. Low (100 micromolar) levels of zinc sulphate (ZnSO4) counteracted glutamate- and NMDA-induced lactate dehydrogenase release in rat cortical cultures; as well as the changes in Gamma-aminobutyric acid (GABA)-immunoreactivity mediated by experimental ischaemia and NMDA in isolated rabbit retinas. However, high (500 micromolar) levels of ZnSO4 caused lactate dehydrogenase release and...