Alternative definition : KEGG: Neurotrophins are a family of trophic factors involved in differentiation and
survival of neural cells. The neurotrophin family consists of nerve growth factor
(NGF), brain derived neurotrophic factor (BDNF), neurotrophin 3 (NT-3), and neurotrophin
4 (NT-4). Neurotrophins exert their functions through engagement of Trk tyrosine kinase
receptors or p75 neurotrophin receptor (p75NTR). Neurotrophin/Trk signaling is regulated
by connecting a variety of intracellular signaling cascades, which include MAPK pathway,
PI-3 kinase pathway, and PLC pathway, transmitting positive signals like enhanced
survival and growth. On the other hand, p75NTR transmits both positive and negative
signals. These signals play an important role for neural development and additional
higher-order activities such as learning and memory.;