Uncovering a critical period of synaptic imbalance during postnatal development of the rat visual cortex: role of brain‐derived neurotrophic factor

摘要

Key points class="unordered" style="list-style-type:disc" id="tjp13176-list-0001">With daily electrophysiological recordings and neurochemical analysis, we uncovered a transient period of synaptic imbalance between enhanced inhibition and suppressed excitation in rat visual cortical neurons from the end of the fourth toward the end of the fifth postnatal weeks.The expression of brain‐derived neurotrophic factor (BDNF), which normally enhances excitation and suppresses inhibition, was down‐regulated during that time, suggesting that this may contribute to the inhibition/excitation imbalance.An agonist of the BDNF receptor tropomyosin‐related kinase B (TrkB) partially reversed the imbalance, whereas a TrkB antagonist accentuated the imbalance during the transient period.Monocular lid suture during the transient period is more detrimental to the function and neurochemical properties of visual cortical neurons than before or after this period.We regard the period of synaptic imbalance as the peak critical period of vulnerability, and its existence is necessary for neurons to transition from immaturity to a more mature state of functioning.