Distribution of parvalbumin-immunoreactive cells and fibers in the monkey temporal lobe: the amygdaloid complex.

The calcium-binding protein parvalbumin was immunohistochemically localized in the monkey amygdaloid complex. Parvalbumin-immunoreactive neuronal cell bodies, fibers, and terminals were observed in several amygdaloid nuclei and cortical areas. Three types of aspiny neurons, ranging from small spherical cells (Type 1) to large multipolar cells (Type 2) and fusiform cells (Type 3) were observed in most amygdaloid regions, though the proportions of the cell types were different in each region. The density of parvalbumin-immunoreactive fibers and terminals tended to parallel the density of labeled cell bodies. The highest densities of parvalbumin profiles were observed in the nucleus of the lateral olfactory tract, the periamygdaloid cortex (PAC2), the magnocellular division of the basal nucleus, the ventrolateral portion of the lateral nucleus, and the accessory basal nucleus. The regions containing the lowest densities of parvalbumin-positive profiles were the medial nucleus, anterior cortical nucleus, central nucleus, and the paralaminar nucleus. In regions with fiber and terminal labeling, pericellular networks of fibers, reminiscent of basket cell terminations, were commonly observed to surround unstained neuronal cell bodies and proximal dendrites. In the magnocellular division of the basal nucleus, and to a lesser extent in the lateral nucleus, parvalbumin-labeled "cartridges" of axo-axonic terminals were observed on the initial segments of unlabeled cells. Parvalbumin-positive varicosities were also commonly observed in close apposition to the soma and dendrites of parvalbumin-immunoreactive cells. Given the close correspondence between the distribution of parvalbumin-positive neurons and a subset of GABAergic neurons in many brain regions, these data provide a first indication of the organization of the inhibitory circuitry of the primate amygdaloid complex.