Modulation of memory using enzymatic digestion of perineuronal nets in perirhinal cortex

In the adult brain, neuronal plasticity is regulated by a specialized structure of extracellular matrix, the perineuronal nets (PNNs), which restrict synaptic plasticity by binding molecules of inhibitory nature and posing as a physical barrier to alterations in neuronal connectivity. This effect is abolished by removal of PNNs by the enzyme chondroitinase ABC (chABC), which enables to reopen critical period window and leads to memory improvement. Here, we utilized chABC and a novel approach in removing the PNNs in perirhinal cortex, using the enzyme hyaluronidase (Hyase), to assess differences in the use of these enzymes in object recognition (OR) memory improvement and alterations in the structure of neuronal network of wild type mice. Our findings suggest that Hyase may be a more convenient tool to PNN removal than chABC, as Hyase surpasses chABC in promoting the OR memory, influence larger portion of neuronal network by affecting both inhibitory and excitatory neurons, and provides extended temporal window for experimental modulation of activity-dependent synaptic plasticity. Key words: perineuronal nets, synaptic plasticity, chondroitinase ABC, hyaluronidase, perirhinal cortex, memor