Distribution of synaptic zinc in the macaque monkey amygdala

Abstract

We have mapped the macaque amygdala for the distribution of synaptic zinc (Zn), a co-factor of glutamate implicated in plasticity, as well as in several excitotoxic and other pathophysiological conditions. In brief, we found that the amygdala is Zn enriched in all nuclear groups (i.e., basolateral and cortical groups, as well as central and medial nuclei) but with marked differences in density. By comparing parallel tissue series histologically reacted for Zn and parvalbumin (PV), we further found that regions high in Zn are typically low in PV neuropil. In the basolateral group, there is a particularly distinct dorsoventral gradation such that Zn levels are most dense ventrally, i.e., in the paralaminar nucleus, the ventral division of the lateral nucleus, and the parvicellular divisions of both the basal nucleus and the accessory basal nucleus. PV levels are least dense in these same regions. For the central and medial nuclei, there is a slight mediolateral gradient, with Zn levels being higher medially. PV is low overall in these nuclei. Electron microscopic results confirmed that Zn is contained in synaptic boutons. These form asymmetrical, presumably excitatory, synapses, and the postsynaptic targets are mainly spines of projection neurons. The inhomogeneous distribution of Zn in the monkey amygdala may be related to different types or degrees of plasticity among the amygdaloid subnuclei. The complementary distribution with PV parallels that of several other substances and is interesting in the context of subnuclear vulnerability for human neuronal disease, such as seizure and Alzheimer's disease.

Differential modes of termination of amygdalothalamic and amygdalocortical projections in the monkey

“…(See Methods, Ichinohe and Rockland [2005a], for further discussion that the signal is Zn, as opposed to other metal ions.) Zhong and Rockland, 2003), and three others (R42, R43, R53) had injections within prefrontal cortex.…”

“…Four brains were available from a previous study, which had been reacted for Zn histochemistry (Ichinohe and Rockland, 2005a). These were examined for area and laminar distribution of Zn-positive (Znϩ) terminations.…”

“…These were examined for area and laminar distribution of Zn-positive (Znϩ) terminations. Briefly, the IntenSE M silver Enhancement kit (Amersham International, Little Chalfont, Bucks, UK) was used to intensify Zn signals (Danscher et al, 1987;De Biasi and Bendotti, 1988;Ichinohe and Rockland, 2005a). Sections were washed thoroughly with 0.1 M PB, followed by 0.01 M PB.…”

Nuclear organization of the rock hyrax (Procavia capensis) amygdaloid complex

“…Whether this is true or not remains to be determined. In the primate amygdaloid complex, a neuronal cluster with a similar appearance and topological location within the accessory basal nuclear cluster to the ABsh described herein for the hyrax has been termed the ventromedial accessory basal nucleus (ABvm) (Pitkänen and Amaral 1993a, b;Sorvari et al 1995;Ichinohe and Rockland 2005). A similar nucleus is not apparent in the accessory basal nuclear cluster in the laboratory rat (e.g.…”

“…In the rock hyrax and the laboratory rat, the relative positions of the nuclear clusters (such as the lateral, basal and accessory basal which run from dorsal to ventral, respectively) are quite similar (Price et al 1987); however, in the macaque monkey and human, the orientation of these (and other) nuclear clusters within the amygdala appear to be oriented orthogonal when compared to the hyrax and rat (e.g. Pitkänen and Amaral 1993a, b;Sorvari et al 1995;Ichinohe and Rockland 2005). This difference in relative location of the nuclear clusters within the amygdala between species appears to be related to the expansion of the temporal lobe.…”