Abstract
Perineuronal nets (PNs) are aggregates of extracellular matrix that have been associated with neuronal plasticity, critical periods, fast-spiking cells and protection from oxidative stress. Although PNs have been reported in the auditory system in several species, there is disagreement about the distribution of PNs within the inferior colliculus (IC), an important auditory hub in the midbrain. Furthermore, PNs in many brain areas are preferentially associated with GABAergic cells, but whether such an association exists in the IC has not been addressed. We used Wisteria floribunda agglutinin staining and immunohistochemistry in guinea pigs to examine PNs within the IC. PNs are present in all IC subdivisions and are densest in the central portions of the IC. Throughout the IC, PNs are preferentially associated with GABAergic cells. Not all GABAergic cells are surrounded by PNs, so the presence of PNs can be used to subdivide IC GABAergic cells into “netted” and “non-netted” categories. Finally, PNs in the IC, like those in other brain areas, display molecular heterogeneity that suggests a multitude of functions.
Highlights
Perineuronal nets (PNs) are aggregates of extracellular matrix molecules that surround a subset of neurons in many regions of the central nervous system
By comparing PN staining with vesicular glutamate transporter 2 (VGLUT2) staining, we demonstrate that VGLUT2–immunopositive rings are present in guinea pigs and are associated primarily with GABAergic cells that have PNs
CHARACTERISTICS OF inferior colliculus (IC) PNs: DISTRIBUTION, ASSOCIATION WITH GABAergic CELLS, AND MOLECULAR HETEROGENEITY WFA-labeled PNs are most dense in central portions of the IC Wisteria floribunda agglutinin-labeled PNs are readily identifiable in the IC as extracellular aggregates of WFA staining around certain neurons
Summary
Perineuronal nets (PNs) are aggregates of extracellular matrix molecules that surround a subset of neurons in many regions of the central nervous system (for review, Celio and Blümcke, 1994; Karetko and Skangiel-Kramska, 2009). The main molecular components of PNs are chondroitin sulfate proteoglycans (CSPGs), such as aggrecan and brevican, which are known to inhibit neurite outgrowth (Hockfield et al, 1990; Yamada et al, 1997; Corvetti and Rossi, 2005; Ajmo et al, 2008). These observations have led to the hypothesis that PNs function to reduce structural plasticity following development. More recent work has expanded the list of functions attributed to PNs, including promotion of synaptic plasticity (Bukalo et al, 2001; de Vivo et al, 2013), protection of neurons from oxidative damage (Suttkus et al, 2012; Cabungcal et al, 2013), and binding molecules for transport into the cell (Beurdeley et al, 2012)
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