Distribution of parvalbumin‐immunoreactive cells and fibers in the human amygdaloid complex

Abstract

The calcium-binding protein, parvalbumin, was localized immunohistochemically in the human amygdaloid complex. Neuronal cell bodies and fibers that are immunoreactive to parvalbumin were observed in most of the amygdaloid nuclei and cortical areas. Three types of immunoreactive aspiny neurons, ranging from small spherical cells (type 1) to large multipolar cells (type 2) and fusiform cells (type 3), were observed. The densities of the types of neurons that were parvalbumin-immunoreactive varied in the different regions of the amygdala. The highest densities of parvalbumin-immunoreactive neurons were observed in the lateral nucleus, in the magnocellular and intermediate divisions of the basal nucleus, in the magnocellular division of the accessory basal nucleus and in the amygdalohippocampal area. The regions containing the lowest density of parvalbumin-immunoreactive cells were the paralaminar nucleus, the parvicellular division of the basal nucleus, the central nucleus, the medial nucleus and the anterior cortical nucleus. In general, the distribution of immunoreactive fibers and terminals paralleled that of immunoreactive cells. Parvalbumin-immunoreactive varicose fibers formed basket-like plexi and cartridges around the unstained neurons, which suggests that parvalbumin is located in GABAergic basket cells and chandelier cells, respectively. The distribution of parvalbumin-immunoreactive profiles in the human amygdaloid complex was similar to, rather than different from that previously reported in the monkey amygdala (Pitkänen and Amaral [1993] J. Comp. Neurol. 331:14-36). This study provides baseline information about the organization of GABAergic inhibitory circuitries in the human amygdaloid complex.

Subpopulations of neurons expressing parvalbumin in the human amygdala

“…In these nuclei, IR puncta were often found to surround unstained somata or to align in "cartridge" formations. These distribution patterns are consistent with those observed in a recent light microscopy study from our laboratory (Berretta et al, manuscript in preparation) and those reported by Sorvari et al (1995). As also described by the same group, PVB-IR neurons in the amygdala were found to be cytoarchitectonically heterogenous.…”

“…These results are in apparent contradiction with a dual-antigen immunocytochemistry study in the rodent amygdala by McDonald and Betette (2001), reporting that 80% of PVB-IR neurons in the amygdala were found to coexpress CB. On the other hand, this estimate is consistent with reports describing the distribution of CB-and PVB-IR neurons in the human amygdala as complementary rather than overlapping (Sorvari et al, 1995(Sorvari et al, ,1996b. On a speculative level, such a contradiction may be explained by evidence suggesting an intriguing trend toward a decrease of PVB-CB coexpression in primate cortical or cortex-like regions compared with equivalent brain regions in rodents.…”

“…2L). Light microscopy analysis showed that the distribution patterns of PVB, CB, and PNNs staining in our tissue correspond well to those detected in the human and monkey amygdala and entorhinal cortex in other laboratories (Hartig et al, 1995;Sorvari et al, 1995Sorvari et al, ,1996bMikkonen et al, 1997). Standard tests for antisera specificity included omission of either the primary or the secondary antisera.…”

“…Among the several subpopulations of interneurons forming these circuits, those expressing the calcium-binding protein parvalbumin (PVB) are localized preferentially within the BLC (Sorvari et al, 1995). These neurons have been shown to affect information processing in this region crucially.…”

“…These neurons were considered "large" if their somata cross-sectional area was more than 120 3m. This classification represents only a slight modification with respect to that proposed by Sorvari et al (1995) and is based on our observations on the size and shape of PVB-and CB-IR neurons in the human amygdala. Crosssectional area for all neurons examined was measured by using the Leica TCS Confocal System, which allows tracing around neuron somata.…”