HISTOCHEMICAL DISTRIBUTION OF ZINC IN THE BRAIN OF THE ZEBRA FINCH (TAENOPYGIA-GUTTATA)

The distribution of zinc was studied in the brain of the zebra finch ( Taenopygia guttata) by means of the selenium histochemical method. A s pecific pattern was seen, which usually correlated with the main known architectonic subdivisions. In addition, a few as yet unidentified st ructures were observed. In the telencephalon, the pallial components w ere stained with moderate to strong intensity. The only exceptions wer e the hyperstriatum intercalatus superior, a small medial area in the hyperstriatum accessorium and in the dorsolateral cortex, and the dors omedial part of the hippocampal complex, which were virtually devoid o f staining. Staining of the dorsal ventricular ridge components varied considerably. The archistriatum, the nucleus accumbens, the nucleus o f the stria terminalis, the hyperstriatum ventrale and the lateral sep tum showed moderate to strong staining. The medial septum was weakly s tained. The neostriatum showed a rather complex pattern of staining wi th unstained areas, such as the magnocellular nucleus of the anterior neostriatum, and other parts intensely stained, especially in its caud al region. Both paleostriatii primitivum and augmentatum showed a rost ro-caudal gradient that was increasingly stained. We also observed an intensely stained area ventral to the fasciculus prosencephali lateral is and lateral to the tractus septomesencephalicus, a weakly to modera tely stained band ventral to the lobus parolfactorius, an intensely st ained zone along the lateral ventricle in the hyperstriatum ventrale, and an unstained almond-shaped nucleus in the lateral hyperstriatum ve ntrale. In the diencephalon, the hypothalamus showed a moderate to str ong, rather uniform staining, whereas the thalamus was usually weakly to moderately stained, with the exception of a few unstained nuclei. O nly the lateral nucleus of the habenula was stained, and with strong i ntensity. Most of the mesencephalon stained rather uniformly with a mo derate to strong intensity. The most intense staining was seen in the substantia grisea centralis, the substantia grisea et fibrosa perivent ricularis, the torus semicircularis and the nucleus intercollicularis. The tectum opticum was virtually devoid of stain except-for two light bands in the stratum griseum et fibrosum superficiale. The formatio r eticularis was moderately stained. All the other structures were eithe r weakly stained or unstained. Some staining was seen in the Purkinje and the granular layers of the cerebellum, as well as around its inter nal nuclei. The pons and the medulla oblongata showed an overall moder ate to intense staining, with the exception of a few unstained nuclei. When compared in three bird species belonging to different genera, zi nc distribution shows remarkable similarities, despite species, age an d methodological differences. The pattern of zinc staining suggests th at this element may play an important role in integrative and autonomi c functions.