HISTOCHEMICAL-DEMONSTRATION OF ZINC IN THE HIPPOCAMPAL REGION OF THE DOMESTIC PIG .3. THE DENTATE AREA

The distribution of zinc was described in the dentate area, a part of the hippocampal region, of the domestic pig. A modification of Timm's sulphide silver procedure, the Neo-Timm method, was used for the histochemical demonstration of zinc. The staining of the dentate area exhibited a well-defined stratified pattern, the predominant part of the staining being restricted to the neuropil, although weakly stained nerve cell bodies were observed in the hilus fasciae dentatae. In the molecular layer, three distinct sublaminae were seen at most septotemporal levels. The outer and inner sublaminae displayed medium staining intensity, whereas the intermediate sublamina appeared extremely pale. The granular cell layer was well stained in its superficial two thirds, because of dense masses of staining occupying the interstices between the unstained granular cells. In the hilus fasciae dentatae, extreme differences in staining intensity were seen between the layers, ranging from very intense staining of the outer hilar cell layer to generally weak staining of the inner plexiform layer. The distribution of zinc in the pig was compared with that in the guinea pig and rat, described previously. The staining pattern of the molecular layer showed striking species differences, whereas the granular cell layer appeared very near identical. The stratified staining pattern seen in the hilus of the pig is very similar to the distribution observed in the guinea pig, but differs from the essentially homogeneous staining of the rat hilus. However, the differences in hilar staining pattern between the pig and guinea pig on the one hand and the rat on the other essentially display variation in the cytoarchitectural organization of the hilus, rather than expressing a true species difference.