The existence of PNNs has been implicated by Golgi, Lugaro, Donaggio, Martinotti, Ramón y Cajal and Meyer. However, Ramón y Cajal credits Golgi with the discovery of PNNs because he was the first to draw attention to them and gave the first precise description in 1893. Moreover, Golgi brought interest to the subject due to his opinion that the PNN was not a neuronal structure but rather a "kind of corset of neurokeratin which impeded the spread of current from cell to cell". Despite debating the topic, Ramón y Cajal claimed that the perineuronal net was simply a staining artifact derived from the coagulation of extracellular fluids. Due to his influential opinion at the time, interest in the topic subsided.
Interest arose in the 1960s when several authors drew attention to the presence of periodic-acid-Schiff-positive (PAS-positive) material surrounding nerve cells. This PAS-positive material was suspected of being composed of negatively charged substances, such as chondroitin sulfate proteoglycans (CSPGs). However, the authors clung to the idea that the material was intricately connected to the blood–brain barrier and failed to see the similarities it had with the perineuronal net described by Golgi. Interest only rose again in the past few decades when it was discovered that PNNs constitute markers for physiologically mature neurons.
Read more about this topic: Perineuronal Net
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