Organization of zinc-containing terminal fields in the brain of the lizard Podarcis hispanica: a histochemical study.

The Timm method for the histochemical detection of metals defines accurately many terminal fields in the brain of mammals. This pattern is based on the presence of zinc within the synaptic vesicles of some boutons. The aim of this study was to use the Timm method for the anatomical description of the brain in a reptile. In the telencephalon, zinc staining was observed in the inner layer of the medial cortex, the inner and outer layers of both dorsomedial and dorsal cortices, the inner layer of the lateral cortex pars anterior ventralis, the lateral cortex pars profunda, the intermediate and caudal aspects of the anterior dorsal ventricular ridge, the marginal layer and hilus of the nucleus sphericus, the perifascicular nucleus of the accessory olfactory tract, the striatum pars medialis, the olfactory tubercle, the septum pars anterior, and embedded in the fibres of both pallial and anterior commissures. In the diencephalon, staining was observed in the ventromedial hypothalamic nucleus and among the fibers of the stria terminalis. Stained somata and dendrites were observed in the infundibulum. In the mesencephalon and rhombencephalon, sparse staining was observed in the central gray, torus semicircularis, nucleus interpeduncularis, raphe, reticular formation, Purkinje and granular cell layers in the cerebellum, and nucleus cerebellaris medialis. The present results suggest that the histochemical detection of zinc may be a useful method for the accurate definition of terminal fields in the brain of reptiles also. The presence of zinc-containing terminal fields is discussed in relation to the connections and histochemistry in the reptilian brain. Similarities in the pattern of staining for zinc between mammals and reptiles are mentioned.