NEUROTROPHIN RELEASE BY NEUROTROPHINS - IMPLICATIONS FOR ACTIVITY-DEPENDENT NEURONAL PLASTICITY

Neurotrophins, secreted in an activity-dependent manner, are thought t o be involved in the activity-dependent refinement of synaptic connect ions. Here we demonstrate that in hippocampal neurons and the rat pheo chromocytoma cell line PC12 application of exogenous neurotrophins ind uces secretion of neurotrophins, an effect that is mediated by the act ivation of tyrosine kinase neurotrophin receptors (Trks). Like activit y-dependent secretion of neurotrophins, neurotrophin-induced neurotrop hin secretion requires mobilization of calcium from intracellular stor es. Because neurotrophins are likely to be released from both dendrite s and axons, neurotrophin-induced neurotrophin release represents a po tential positive feedback mechanism, contributing to the reinforcement and stabilization of synaptic connections.