A heavy metal marker of the developing striatal mosaic.

The pattern of distribution of heavy metals in the developing rat striatum was examined using the sulphide silver histochemical method of Timm. The staining was very weak on postnatal day 3 but by day 6 was found in distinct patches. The staining had assumed a fairly homogeneous distribution by day 11 similar to that seen in the adult. This appeared to be due to an increased staining in the matrix, rather than a reduction in the patches, some of which could still be discerned even in the adult. The Timm-stained patches present on day 6 corresponded to the tyrosine hydroxylase immunoreactive patches which have been previously described in the developing striatum. Since zinc appears to be the principal metal detected by the Timm method in brain, the Timm staining pattern seen in the present study may be related to a zinc-growth factor complex in the developing striatum.