Subpopulations of neurons expressing parvalbumin in the human amygdala

Abstract

Amygdalar intrinsic inhibitory networks comprise several subpopulations of γ-aminobutyric acidergic neurons, each characterized by distinct morphological features and clusters of functionally relevant neurochemical markers. In rodents, the calcium-binding proteins parvalbumin (PVB) and calbindin D28k (CB) are coexpressed in large subpopulations of amygdalar interneurons. PVBimmunoreactive (-IR) neurons have also been shown to be ensheathed by perineuronal nets (PNN), extracellular matrix envelopes believed to affect ionic homeostasis and synaptic plasticity. We tested the hypothesis that differential expression of these three markers may define distinct neuronal subpopulations within the human amygdala. Toward this end, triple-fluorescent labeling using antisera raised against PVB and CB as well as biotinylated Wisteria floribunda lectin for detection of PNN was combined with confocal microscopy. Among the 1,779 PVB-IR neurons counted, 18% also expressed CB, 31% were ensheathed in PNN, and 7% expressed both CB and PNN. Forty-four percent of PVB-IR neurons did not colocalize with either CB or PNN. The distribution of each of these neuronal subgroups showed substantial rostrocaudal gradients. Furthermore, distinct morphological features were found to characterize each neuronal subgroup. In particular, significant differences relative to the distribution and morphology were detected between PVB-IR neurons expressing CB and PVB-IR neurons wrapped in PNNs. These results indicate that amygdalar PVB-IR neurons can be subdivided into at least four different subgroups, each characterized by a specific neurochemical profile, morphological characteristics, and three-dimensional distribution. Such properties suggest that each of these neuronal subpopulations may play a specific role within the intrinsic circuitry of the amygdala. Keywordscalbindin D28k; perineuronal nets; immunocytochemistry; confocal microscopy; basolateral complex of the amygdala The basolateral complex of the amygdala (lateral, basolateral, and accessory basal nuclei; BLC) plays an important role in assigning affective and motivational significance to sensory inputs, forming emotional memories, and generating emotional responses (Gloor, 1986;Halgren, 1992;Brothers, 1990;LeDoux, 1992;Aggleton, 1993;Adolphs et al., 1994). Complex intrinsic inhibitory circuits are believed to represent a critical component of the neural networks NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript underlying these functions. 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. For instance, the extremely low spontaneous firing rates typical of BLC projection neurons are thought to be the result of strong intrinsic inhibitory pressures originating from PVB-immunoreactive (-IR) neurons (Rainnie et al., 1991;Par...

Total number, distribution, and phenotype of cells expressing chondroitin sulfate proteoglycans in the normal human amygdala

“…Perineuronal nets showed evident hollow, mesh-like appearance and neuron-like shape (Fig 1A&B). Their morphological features suggests preferential association with large multipolar neurons, confirming previous reports in human and nonhuman primate amygdala (Hartig, et al, 1995,Pantazopoulos, et al, 2006. WFA intracellular labeling was not detected in cells with typical neuronal morphology.…”

“…Only few nets were detected in the ABN (18,096 ± 21,208) and CO (15,496 ± 8,348). As reported previously (Pantazopoulos, et al, 2006), and shown as an example in Fig. 2, perineuronal nets tend to cluster along the lateral portion of the LN, and in the magnocellular BN region.…”

“…The distribution of perineuronal nets in this nuclear complex, previously reported in human as well as monkey (Hartig, et al, 1995, Pantazopoulos, et al, 2006, shows preferential concentration in the LN (408,720 ± 300,669), followed by the BN (72,696 ± 72,239). Only few nets were detected in the ABN (18,096 ± 21,208) and CO (15,496 ± 8,348).…”

“…The lectin wisteria floribunda agglutinin, as well as other plant-derived lectins, binds to the N-acetyl-galactosamine component of the chondroitin sulfate chains and represents a useful tool to detect CSPGs in brain tissue (Bruckner, et al, 1993, Celio, et al, 1998, Hartig, et al, 1992, Nakagawa, et al, 1986, Pantazopoulos, et al, 2006. In adult rodents, CSPGs secreted in the ECM, and associated with perineuronal nets, are synthesized and expressed by several different cell types, including neurons, astrocytes, oligodendrocytes and NG2-expressing oligodendrocyte precursor cells , Hamel, et al, 2005, John, et al, 2006, McKeon, et al, 1999, Thon, et al, 2000, Viapiano, et al, 2006.…”

“…Ternary complexes composed of CSPGs, hyaluronic acid, and glycoproteins are the main components of pericellular aggregates known as perineuronal nets (Celio, et al, 1998, Deepa, et al, 2006, Yamaguchi, 2000. These nets are dense, mesh-like 'gloves' found to surround the soma, primary dendrites and initial axonal segment of distinct neuronal populations, the most well-studied of which is a group of fastspiking neurons expressing the calcium binding protein parvalbumin (Berghuis, et al, 2004, Bruckner, et al, 2006, Morris, et al, 2000, Pantazopoulos, et al, 2006. Current evidence suggests that perineuronal nets form gradually around successful synaptic connections and may restrict further changes of those synapses (Dityatev, et al, 2003).…”