Altered laminar distribution of hippocampal zinc in mutant mice lacking neuronal nitric oxide synthase. A histochemical study.

The recently discovered role of nitric oxide (NO) in the accumulation of zinc in the central nervous system encouraged us to compare the distribution of zinc in the hippocampal formation and other brain regions of nitric oxide synthase knockout with wild-type mice. The histochemical Timm's staining technique was used. While no changes in the patterns of zinc staining were observed in extrahippocampal brain areas, lamina-specific differences appeared in the distribution of the metal in hippocampi of normal and mutant mice. Less Timm's stainable zinc was detected in the neuropil of strata oriens and radiatum and a loss of Timm's-stained infrapyramidal fibers in knockout mice. The hilar region as well as the suprapyramidal and intrapyramidal blades of the mossy fiber system did not differ between mutant and wild-type mice. Our data show that life-long withdrawal of neuronal-derived NO has effects on the accumulation of zinc in the hippocampal formation of mice.