Neurotrophin action on a rapid timescale

Mechanisms underlying the fast action of neurotrophins include intracellular Ca ²⁺ signaling, neuronal excitation, augmentation of synaptic excitation by modulation of N-methyl-d-aspartate receptor activity and control of synaptic inhibition through the regulation of the K ⁺-Cl ^- cotransporter KCC2. The fastest action of brain-derived neurotrophic factor and neurotrophin-4/5 occurs within milliseconds, and involves activation of TrkB and the opening of the Na ⁺ channel Na _v1.9. Through these rapid actions, neurotrophins shape neuronal activity, modulate synaptic transmission and produce instructive signals for the induction of long-term changes in the efficacy of synaptic transmission.