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Z. Q. Yin, S. Zheng; GABAergic Neurons Co-Localize With Perineuronal Nets and tPA Immunoreactivity in Rat Visual Cortex During Postnatal Development. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3620.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the co-localization of GABAegic neurons, which are increasingly embraced by perineuronal nets (PNNs) composed mainly of chondroitin sulphate proteoglycans (CSPGs) towards the end of the critical period (CP) and Tissue-type plasminogen activator (tPA), a major serine protease in mammalian postnatal brain, plays a key role in mediating ocular dominance shifts in response to monocular deprivation during the CP of visual plasticity; possibly via proteolytic activities on the extracellular matrix in the rat visual cortex during postnatal development.
Long Evans rats of either sex at post-natal weeks three ( PW3), PW5, PW7 and PW14 were transcardially perfused with saline followed 4% paraformaldehyde in 0.1 M PB. Coronal sections (30 µm) of the visual cortex were triple labeled using fluorescent markers to tPA (rabbit anti-murine tPA antibody; American Diagnostica, Stamford), GABA (mouse anti-rat parvalbumin antibody; Sigma, US) and CSPGs in PNNs (biotinylated Wisterla Floribunda Lectin, WFA, Vector, US). The slides were examined using a confocal microscope and sampled fields photographed. Image Proplus 4.5 was used to quantify the density of labeled cells (at least 9 sample boxes, 625 µm2/box). The data were evaluated by one-way ANOVA and LSD multiple comparison t-tests (mean ± SD).
GABAergic neurons were positively labeled for both PNNs and tPA immunoreactivity in the visual cortex at PW 3, PW 5, PW 7 and PW14. The ratio of GABA_ PNNs_ tPA+ neurons to GABAergic neurons that were co-localized with PNNs decreased throughout postnatal development. In the visual cortex of PW3 rats, over 85% of GABAergic neurons that were co-localized with PNNs contained tPA; this decreased to 60%, 50% and 45% at PW5, PW7 and PW14 respectively. The cell density of GABA_tPA- neurons that were co-localized with PNNs significantly increased with age (PW3 20.7 ± 5.4/mm2; PW5 101.1 ± 34.2/mm2; PW7 140.6 ± 44.9/mm2; PW14 188.4 ± 52.9/mm2; one way analysis of variance, ANOVA, P<0.05).
Previous work showed that GABAergic neurons in the rat visual cortex co-localize with PNNs. This study demonstrates that there are GABAergic neurons which are co-localized with PNNs and are either tPA+ or tPA-. The time course of these changes coincides with the rat’s cortical CP between PW3 to PW6. The GABA_tPA+ neurons co-localized with PNNs may be a new subtype of GABAergic neurons that may be involved in visual cortical synaptic plasticity due to the function(s) of tPA.
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