The Study On Local Action Modes Of Neurotrophic Factors

In the developing vertebrate nervous system, neurons are produced in vast excess. Within a restricted time period, the majority of neurons undergo naturally-occuring cell death due to no contact with targets, only small number of neurons innervated into the target fields can survive. The classical theory indicates limited target-derived neurotrophic factors mediate the survival of neurons. But neurons before innervation of target fields and neurons discontacted with target cells in mature nervous system yet can be survived. It indicates no all survival phenomena can be explained by target-derived mechanism of NTFs. Many studies reported suggest both neuronal precursor cells before innervation of target fields and the neurons of adult animal coexpress neurotrophic factors and their receptors, implying that autocrine and paracrine modes of NTFs exit. It has been observed that a number of neurotrophic factors and their receptors were expressed in cultured hippocampal cells and dorsal root ganglionic cells. To enhance or block the expressing of these factors will promote or suppress the survival of these neurons, indicating that the phenomena of autocrine and paracrine modes of neurotrophic factors are universal and they play an important role in the development, plasticity and homeostasis of nervous system. The neurotrophic factors might exert trophic effects by local action modes including autocrine and paracrine modes, target-derived mode and others, contingent upon different time and space in the development. Different modes of NTFs might have mutual synergy and conversion.NT3 and CNTF are two completely different neurotrophic factors in amino acid composition, receptor components and signal transduction. They have overlapping trophic effects, with similar biological...