Expression of Perineuronal Nets, Parvalbumin and Protein Tyrosine Phosphatase σ in the Rat Visual Cortex During Development and After BFD

Purpose of the Study: Protein tyrosine phosphatase sigma (PTP sigma) acts as a neuronal receptor for chondroitin sulfate proteoglycans (CSPGs). CSPGs have inhibitory effects on experience-dependent plasticity and usually form lattice-like cell coatings that surround the parvalbumin (PV) interneurons in the visual cortex (VC). We investigated developmental changes and the effect of binocular form deprivation (BFD) on PTP sigma, perineuronal nets (PNNs) and their tempo-spatial relationships with PV neurons in the VC. Materials and Methods: Double-immunostaining was used to observe the coexpression pattern of PNNs staining by biotinylated wisteria floribunda lectin (WFA) with PV neurons. The expression of PTP sigma in the VC of Long Evans rats was detected by real-time quantitative PCR, immunohistochemistry and western blots. The changes in the number of PV/WFA/PTP sigma labeled cells in layer IV of the VC and its proportion of PV neurons were examined during development and after BFD. Results: The expression of PV neurons wrapped by PNNs was increased, particularly in the first half of the critical period, and the ratio for PV neurons reached the highest level (over 75%) at adulthood, indicating that PNNs may play an important role in the maturation of PV neurons during the critical period. BFD decreased the density of PNNs and the percentage of PV neurons with PNNs. This result suggests that the number of PNNs surrounding PV neurons may be experience-dependent. Meanwhile, the CSPG receptor PTP sigma was maintained at its lowest level during the critical period and could be modulated by BFD after the critical period. The percentage of PV/WFA/PTP sigma-positive cells in PV population increased during development and reached its highest ratio at adulthood, which could also be reversed by BFD. Conclusions: The changes in the coexpression of PNNs, PV and PTP sigma provide valuable insights into the connection between CSPGs and PV neurons.