Distribution of neurons of origin of zinc-containing projections in the amygdala of the rat.

The present study describes the distribution of neurons of origin of zinc-containing pathways in the amygdaloid complex of the rat, using the selenium method for simultaneous retrograde labeling of all zinc-containing neurons. With this method, vesicular ionic zinc is precipitated intravitally with selenium compounds and transported retrogradely to the parent neurons, where it can be visualized by silver amplification. Neurons labeled retrogradely with silver-amplified precipitate were observed in all amygdaloid nuclei except for the lateral olfactory tract nucleus, the accessory olfactory tract nucleus and the central nucleus. Very few labeled cell bodies were seen in the anterior amygdaloid area and the medial nucleus. The amygdalo-hippocampal area and the amygdalo-piriform transition area both showed a substantial number of labeled somata throughout their rostrocaudal extent. In the anterior cortical nucleus, very few labeled cell bodies were found in the rostral pole, whereas they were abundant in the caudal quarter of the nucleus. In the posterolateral cortical nucleus, the number of labeled cell bodies increased gradually; there were none in the rostral pole, but most of the neurons in the caudal part were labeled. The posteromedial cortical nucleus contained a great number of labeled somata, but with some variation in the rostrocaudal extent of the nucleus. Considerable numbers of labeled neurons were observed throughout the lateral nucleus. In the basolateral nucleus, a small number of labeled cell bodies was present in the rostral half, but a gradual increase was observed in the caudal direction. Finally, in the basomedial nucleus, very few labeled cell bodies were present in the rostral two-thirds, whilst a considerable number was encountered in the caudal one-third. Possible functional implications of neuronal zinc are considered. The distribution of neurons of origin of zinc-containing projections has been compared with previously described intrinsic connections of the rat amygdala, and tracts that may possibly be zinc-containing are outlined and discussed. It is concluded that in all probability a substantial proportion of the intrinsic connectivity of the rat amygdaloid complex is zinc-containing.

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 specific pattern was seen, which usually correlated with the main known architectonic subdivisions. In addition, a few as yet unidentified structures were observed. In the telencephalon, the pallial components were stained with moderate to strong intensity. The only exceptions were the hyperstriatum intercalatus superior, a small medial area in the hyperstriatum accessorium and in the dorsolateral cortex, and the dorsomedial part of the hippocampal complex, which were virtually devoid of staining. Staining of the dorsal ventricular ridge components varied considerably. The archistriatum, the nucleus accumbens, the nucleus of the stria terminalis, the hyperstriatum ventrale and the lateral septum showed moderate to strong staining. The medial septum was weakly stained. The neostriatum showed a rather complex pattern of staining with unstained areas, such as the magnocellular nucleus of the anterior neostriatum, and other parts intensely stained, especially in its caudal region. Both paleostriatii primitivum and augmentatum showed a rostro-caudal gradient that was increasingly stained. We also observed an intensely stained area ventral to the fasciculus prosencephali lateralis and lateral to the tractus septomesencephalicus, a weakly to moderately stained band ventral to the lobus parolfactorius, an intensely stained zone along the lateral ventricle in the hyperstriatum ventrale, and an unstained almond-shaped nucleus in the lateral hyperstriatum ventrale. In the diencephalon, the hypothalamus showed a moderate to strong, rather uniform staining, whereas the thalamus was usually weakly to moderately stained, with the exception of a few unstained nuclei. Only the lateral nucleus of the habenula was stained, and with strong intensity. Most of the mesencephalon stained rather uniformly with a moderate to strong intensity. The most intense staining was seen in the substantia grisea centralis, the substantia grisea et fibrosa periventricularis, 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 reticularis was moderately stained. All the other structures were either weakly stained or unstained. Some staining was seen in the Purkinje and the granular layers of the cerebellum, as well as around its internal nuclei. The pons and the medulla oblongata showed an overall moderate to intense staining, with the exception of a few unstained nuclei. When compared in three bird species belonging to different genera, zinc distribution shows remarkable similarities, despite species, age and methodological differences.(ABSTRACT TRUNCATED AT 400 WORDS)