Research ReportDistribution of pyramidal cells associated with perineuronal nets in the neocortex of rat
Introduction
More than hundred years after their discovery (Golgi, 1893, Ramón y Cajal, 1898), the morphological and functional characterization of perineuronal nets (PNs) of the extracellular matrix gained increasing interest among neuroscientists. Despite series of thorough and versatile investigations, the role of these neuron-associated sheaths is not clear (Celio and Blümcke, 1994, Celio et al., 1998). PNs function has been implicated in synaptic stabilization and in depression of synaptic plasticity (Hockfield et al., 1990, Lander et al., 1997, Fox and Caterson, 2002, Pizzorusso et al., 2002), in the support of ion homeostasis around highly active neurons (Brückner et al., 1993, Brückner et al., 1996a, Brückner et al., 1996b, Brückner et al., 2006, Härtig et al., 1999, Härtig et al., 2001, Hobohm et al., 1998) or in neuroprotection (Brückner et al., 1999, Schüppel et al., 2002, Morawski et al., 2004). The functional significance of this specialized neuronal environment has been suggested and supported by morphological findings describing the location, structure and composition of PNs. They ensheath the perikaryon, proximal parts of dendrites, the axon initial segment and the presynaptic boutons attached to these structures (Hendry et al., 1988, Brückner et al., 1993, Brückner et al., 1996b, Brückner et al., 2006). The main components of PNs are polyanionic chondroitin sulfate proteoglycans (CSPG) and associated molecules such as hyaluronic acid and tenascins (Brückner et al., 1993, Brückner et al., 2000, Köppe et al., 1997, Hagihara et al., 1999, Matsui et al., 1998, Matthews et al., 2002). Lectins, such as Wisteria floribunda agglutinin (WFA), are established markers for PNs for their strong affinity to N-acetylgalactosamine, which is a constituent amino sugar of glycosaminoglycan chains of CSPG (Härtig et al., 1992).
Further advances revealed that PNs in the cerebral cortex are primarily associated with GABAergic interneurons (Brückner et al., 1994, Mulligan et al., 1989, Naegele et al., 1988, Nakagawa et al., 1987) most of which express the calcium-binding protein parvalbumin (Kosaka and Heizmann, 1989, Härtig et al., 1992, Morino-Wannier et al., 1992). However, PNs labeled with WFA or the lectin Vicia villosa were detected around pyramidal neurons as well in different mammalian species, but these perineuronal sheaths were in most cases less established, hence, faintly stained (Ohyama and Ojima, 1997, Brückner et al., 1999, Härtig et al., 1999). Previous studies revealed regional differences in the occurrence and frequency of PNs: primary sensory or motor areas contain considerably more net-associated pyramidal cells (naPCs) than secondary or higher order association areas (Hendry et al., 1988, McGuire et al., 1989, Hausen et al., 1996, Brückner et al., 1999). However, further characterization of different pyramidal cell populations in relation to PNs has only begun (Hendry et al., 1988, Ohyama and Ojima, 1997, Wegner et al., 2003). Similarly, a complete and comprehensive description of the association of PNs to pyramidal cells as well as to their various projection types in rat neocortex has been lacking.
The present study quantitatively analyzes naPCs in the rat neocortex and investigates the association of pyramidal neurons with different projection patterns to the presence of perineuronal sheath in the neocortex of the rat.
Section snippets
Quantitative analysis of the density of naPCs in the various cortical areas
Following WFA histochemistry, naPCs were found in different number and density in the distinct cortical areas (Fig. 1, Fig. 2, Table 1, Table 2). The frequency of naPCs was characterized by the number of naPCs per 1 mm2 (Table 2). Brain regions could be classified into five groups according to their relative density of naPCs. Primary and secondary visual cortices (V1 and V2, respectively) had the highest density values, primary auditory (Au1) had high/medium, the parietal association cortex
Discussion
Previous studies have offered thorough descriptions of PNs around cortical GABAergic interneurons (Brückner et al., 1994, Mulligan et al., 1989, Naegele et al., 1988, Nakagawa et al., 1987) and suggested versatile implications in cell functions including synaptic plasticity, neuroprotection or ion homeostasis (Brückner et al., 1993, Brückner et al., 1996a, Brückner et al., 1996b, Brückner et al., 1999, Pizzorusso et al., 2002). Whereas subtle details of PNs of interneurons have been
Animals
Seventeen five-months-old Wistar rats of both sexes were used. Treatment of animals was in accordance with the Ethical guideline of SOTE and the European Communities Council Directive (86/609/EEC; November 24, 1996).
WFA histochemistry
Five rats were perfused transcardially in deep anesthesia, first with saline (0.9% NaCl) for 1–2 min and then with a fixative containing 4% paraformaldehyde and 0.1% glutaraldehyde in 0.1 M phosphate buffer (pH 7.4) for 30 min. The brains were postfixed in a fixative containing 4%
Acknowledgments
We are grateful for Dr. Gábor Gerber, Dr. Márk Kozsurek and Dr. József Takács for generously providing us the animals used in this study. We would like to thank Dr. Markus Morawski, Dr. László Négyessy and Dr. Zita Puskár for his useful advises. This study was supported by the Basic Research Foundation of Hungary (grant OTKA F 048350), the Hirnliga e.V. and by the Interdisziplinäres Zentrum für Klinische Forschung (IZKF) Leipzig at the Faculty of Medicine of the Universität Leipzig (C1).
References (45)
- et al.
In vivo and in vitro labelling of perineuronal nets in rat brain
Brain Res.
(1996) - et al.
Cortical areas abundant in extracellular matrix chondroitin sulphate proteoglycans are less affected by cytoskeletal changes in Alzheimer's disease
Neuroscience
(1999) - et al.
Axon initial segment ensheathed by extracellular matrix in perineuronal nets
Neuroscience
(2006) - et al.
Perineuronal nets—A specialized form of extracellular matrix in the adult nervous system
Brain Res. Brain Res. Rev.
(1994) - et al.
Perineuronal nets: past and present
Trends Neurosci.
(1998) - et al.
Cortical neurons immunoreactive for the potassium channel Kv3.1b subunit are predominantly surrounded by perineuronal nets presumed as a buffering system for cations
Brain Res.
(1999) - et al.
Perineuronal nets in the rat medial nucleus of the trapezoid body surround neurons immunoreactive for various amino acids, calcium-binding proteins and the potassium channel subunit Kv3.1b
Brain Res.
(2001) - et al.
A metabolic map of cytochrome oxidase in the rat brain: histochemical, densitometric and biochemical studies
Neuroscience
(1995) - et al.
Low expression of extracellular matrix components in rat brain stem regions containing modulatory aminergic neurons
J. Chem. Neuroana.
(1998) - et al.
Cellular distribution of the calcium-binding proteins parvalbumin, calbindin, and calretinin in the neocortex of mammals: phylogenetic and developmental patterns
J. Chem. Neuroanat.
(1999)
Selective staining of a population of parvalbumin-containing GABAergic neurons in the rat cerebral cortex by lectins with specific affinity for terminal N-acetylgalactosamine
Brain Res.
Occurrence of a N-terminal proteolytic fragment of neurocan, not a C-terminal half, in a perineuronal net in the adult rat cerebrum
Brain Res.
Perineuronal nets potentially protect against oxidative stress
Exp. Neurol.
Perineuronal nets of extracellular matrix around hippocampal interneurons resist destruction by activated microglia in trimethyltin-treated rats
Brain Res.
Histochemical demonstration of sensory maps in the rat and mouse cerebral cortex
Brain Res.
Diffuse perineuronal nets and modified pyramidal cells immunoreactive for glutamate and the GABA(A) receptor alpha1 subunit form a unique entity in rat cerebral cortex
Exp. Neurol.
Perineuronal nets provide a polyanionic, glia-associated form of microenvironment around certain neurons in many parts of the rat brain
Glia
Cortical areas are revealed by distribution patterns of proteoglycan components and parvalbumin in the Mongolian gerbil and rat
Brain Res.
Extracellular matrix organization in various regions of rat brain grey matter
J. Neurocytol.
Cortical perineuronal nets in the gray short-tailed opossum (Monodelphis domestica): a distribution pattern contrasting with that shown in placental mammals
Anat. Embryol.
Postnatal development of perineuronal nets in wild-type mice and in a mutant deficient in tenascin-R
J. Comp. Neurol.
The organization and mutability of the forepaw and hindpaw representations in the somatosensory cortex of the neonatal rat
J. Comp. Neurol.
Cited by (68)
Fingolimod increases parvalbumin-positive neurons in adult mice
2022, IBRO Neuroscience ReportsPerineuronal net abnormalities in Slc13a4<sup>+/−</sup> mice are rescued by postnatal administration of N-acetylcysteine
2021, Experimental NeurologyCitation Excerpt :Perineuronal nets (PNNs) are specialized ECM structures composed of hyaluronan, CSPGs (with various core proteins aggrecan, brevican, neurocan, versican, phosphocan), tenascins and link proteins (Bitanihirwe and Woo, 2014; Sorg et al., 2016). Secreted from neurons and glial cells, the ECM constituents of PNNs form a stable lattice like structure (Franco and Muller, 2011; Frantz et al., 2010) and ensheath the soma, dendrite and axon processes of neurons (Alpar et al., 2006; Bruckner et al., 2006). Fast spiking, calcium dependent, parvalbumin (PV)+ GABAergic interneurons are the most prominent cells to be decorated by PNNs and they have significant roles in the maintenance and timing of critical period plasticity (Levelt and Hubener, 2012; Takesian and Hensch, 2013).
Pyramidal neurons: Physiology, pathophysiology, and postnatal development
2021, Factors Affecting Neurodevelopment: Genetics, Neurology, Behavior, and DietChondroitin sulfate proteoglycan-5 forms perisynaptic matrix assemblies in the adult rat cortex
2020, Cellular SignallingModulation of CA2 neuronal activity increases behavioral responses to fear conditioning in female mice
2019, Neurobiology of Learning and MemoryCitation Excerpt :Similarly, if activity of amygdala neurons was increased by hM3Dq in CA2 during training, the cued fear engram may have been more strongly encoded in hM3Dq animals than in control animals, thereby enhancing cued fear memory both two days and two weeks after training. In addition, perineuronal nets (PNNs) are heavily expressed in CA2 (Carstens, Phillips, Pozzo-Miller, Weinberg, & Dudek, 2016), similar to expression observed in several cortical regions (Alpár, Gärtner, Härtig, & Brückner, 2006). Interestingly, PNNs in auditory cortex are regulated by fear conditioning in that mRNA of several PNN components has been shown to be increased four hours after training (Banerjee et al., 2017).