ANTEROGRADE TRANSPORT OF NEUROTROPHINS AND AXODENDRITIC TRANSFER IN THE DEVELOPING VISUAL-SYSTEM

Neurotrophic factors support the differentiation and survival of neuro ns(1,2) and influence properties of synaptic transmission(3,4). The ne urotrophic hypothesis postulates a retrograde action of trophic factor s: their production and release by target cells and their uptake by in nervating axons(5). Besides the retrograde route of trophic messengers , the survival of neurons and the development of synapses is thought t o be also regulated by anterograde, afferent trophic signals(6-10). We now show that exogenous neurotrophins are transported in the anterogr ade direction, from cell bodies to the axon terminals, and that the in tact neurotrophin is released after anterograde transport, taken up an d utilized by second-order visual neurons in the developing chick brai n. These results suggest that anterogradely transported neurotrophins may play a role in synaptic plasticity and may have effects at more th an one synapse beyond the initial release site.