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Neurotrophins are a subgroup of growth factors acting within the nervous system. They are small proteins forming a family of several members. Among these, NT-3 is the most abun­dantly distributed within the developing and mature nervous system. NT-3 significantly contributes to the formation and maintenance of the nervous system and may be involved in various neurological diseases. In the future, it may also become a therapeutic agent for their treatment, therefore the mechanisms of its action are intensely investigated. The aim of our study was to investigate the effects of NT-3 on the ability of motor neurons to form functional neuromuscular junctions. An in vitro experimental model in which neurons extend­ing from rat spinal cord explants form functional neuromuscular junctions onto human myotubes has been employed for this purpose. The effects of NT-3 were quantitatively deter­mined by 1) counting neuronal outgrowths from the spinal cord explants 2) determining the percentage of contraction-positive explants 3) counting the number of contracting units per explant and 4) counting the number of nicotinic receptor clusters at neuromuscular junc­tions using rhodamine-labelled a-bungarotoxin. The statistical significance of differences between the treated and control groups of explants was tested using the independent sam­ples Student t-test. NT-3 added to the culture medium at the concentration of 10 ng/ml, which proved the most efficient in our concentration testing, increased all the parameters of func­tional innervation. A higher capacity of the neurons to form functional neuromuscular junctions in NT-3-containing cocultures was thus demonstrated.