A hybrid protein (GFP-TTC) comprising the non-toxic proteolytic C fragment of tetanus toxin fused to green fluorescent protein was used to analyze the functional synaptic organization of neural networks. When injected intramuscularly in vivo, the GFP-TTC hybrid protein binds to tetanus neurotoxin receptors and clusters very rapidly to the active neuromuscular junction. Membrane traffic by GFP-TTC at the pre-synaptic level of the neuromuscular junction is strongly and rapidly influenced by exogenously co-injecting neurotrophic factors, such as BDNF, NT-4, and GDNF, but not by NGF, NT-3, and CNTF. The membrane traffic, directly detected using GFP-TTC in vivo, permits methods of analyzing synaptic functioning as well as methods of modulating neuronal transport using neurotrophic factors and agonists or antagonists thereof.
In vivo modulation of neuronal transport