Distribution of histochemically reactive zinc in the forebrain of the rat.

The major cytoarchitectonic regions of the rat brain that stain with the Timm-Danscher metal stain were tested with the fluorescent probe for zinc, 6-methoxy 8-para toluene sulfonamide quinoline (TSQ). Throughout most of the striatum, cerebral cortex and limbic system, the diffuse, even neuropil staining produced by the Timm-Danscher method was mirrored by comparable fluorescence in TSQ-stained sections. Blockade of the TSQ fluorescence by prior treatment with sulphide indicated that the Timm-Danscher and the TSQ procedures both labeled the same pool of endogenous metal, which is inferred to be the zinc that is in axonal boutons. It is concluded that the Timm-Danscher staining generally indicates zinc-containing axonal boutons. The distribution of the zinc-containing axonal boutons throughout the forebrain is described.