Pro-Brain-Derived Neurotrophic Factor (proBDNF)-Mediated p75NTR Activation Promotes Depolarizing Actions of GABA and Increases Susceptibility to Epileptic Seizures

The brain-derived neurotrophic factor (BDNF) is synthesized as a precursor, namely proBDNF, which can be processed into mature BDNF (mBDNF). Evidences suggest that proBDNF signaling through p75(NTR) may account for the emergence of neurological disorders. These findings support the view that the relative availability of mBDNF and proBDNF forms is an important mechanism underlying brain circuit formation and cognitive functions. Here we describe novel insights into the proBDNF/p75(NTR) mechanisms and function in vivo in modulating neuronal circuit and synaptic plasticity during the first postnatal weeks in rats. Our results showed that increased proBDNF/p75(NTR) signaling during development maintains a depolarizing.-aminobutyric acid (GABA) response in a KCC2-dependent manner in mature neuronal cells. This resulted in altered excitation/inhibition balance and enhanced neuronal network activity. The enhanced proBDNF/p75(NTR) signaling ultimately led to increased seizure susceptibility that was abolished by in vivo injection of function blocking p75(NTR) antibody. Altogether, our study shed new light on how proBDNF/p75(NTR) signaling can orchestrate the GABA excitatory/inhibitory developmental sequence leading to depolarizing and excitatory actions of GABA in adulthood and subsequent epileptic disorders.