Neurotrophins and Their Receptors Mediate Processes of Metaplasticity and Long-Term Memory Formation

In this chapter, a special class of small secretory peptides, the neurotrophins and their receptors, will be introduced as candidate molecules in order to calibrate and possibly consolidate memory contents. Numerous reports show that in particular, the neurotrophin brain-derived neurotrophic factor (BDNF) and its TrkB receptor are mediators of positive structural and functional plasticity in the developing and adult nervous system, whereas the p75 neurotrophin receptor might mediate age-related decline in memory function. In the context of memory consolidationConsolidation and long-lasting synaptic plasticitySynaptic plasticity, it is noteworthy that BDNF is discussed as an important transformer of functional into structural changes via trkB receptors, whereas the p75NTR might mediate negative plasticity. Results presented here suggest that BDNF indeed has a functional and specific role in the consolidation of synaptic plasticity and may exert this role by stimulating the local (dendritic) production of plasticity-related proteins (PRPs). BDNF might indeed be itself a PRP, and it might be able to orchestrate the plasticity threshold for a whole cluster of synapses and might, therefore, be involved in processes of metaplasticity and homeostasis as well. This is also of relevance for the aging brain, in which BDNF levels are lower and synaptic tagging compromised.