Effects of binocular form deprivation on the excitatory post-synaptic currents mediated by N-methyl-D-aspartate receptors in rat visual cortex

Expression of perineuronal nets, parvalbumin and protein tyrosine phosphatase σ in the rat visual cortex during development and after BFD

Abstract Purpose of the Study: Protein tyrosine phosphatase σ (PTPσ) 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 PTPσ, 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 PTPσ 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/PTPσ 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 PTPσ 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/PTPσ-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 PTPσ provide valuable insights into the connection between CSPGs and PV neurons.

Binocular form deprivation influences the visual cortex

α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors are considered to play a crucial role in synaptic plasticity in the developing visual cortex. In this study, we established a rat model of binocular form deprivation by suturing the rat binocular eyelids before eye-opening at postnatal day 14. During development, the decay time of excitatory postsynaptic currents mediated by α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors of normal rats became longer after eye-opening; however, the decay time did not change significantly in binocular form deprivation rats. The peak value in the normal group became gradually larger with age, but there was no significant change in the binocular form deprivation group. These findings indicate that binocular form deprivation influences the properties of excitatory postsynaptic currents mediated by α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors in the rat visual cortex around the end of the critical period, indicating that form stimulation is associated with the experience-dependent modification of neuronal synapses in the visual cortex.