EN
The importance of neurotrophin 3 (NT-3) for motor control prompted us to ask whether direct low-threshold electrical stimulation of the tibial nerve aimed at activation of Ia fibers, could increase the pool of NT-3 and its receptor TrkC in the Hoffmannreflex circuitry of the soleus (Sol) muscle. The effects were compared with those on BDNF and its TrkB receptor. Cuff-electrode over the tibial nerve was used to deliver continuous bursts of stimuli in awake rats. Functional mapping of neuronal activation with c-Fos showed that a number of spinal neurons was activated by Ia stimuli. Stimulation produced a strong increase of NT-3 protein (ELISA), in L3- 6 spinal segments and in Sol with minor effect on BDNF level in L3-6. Protein level of NT-3 and BDNF corresponded to the changes of NT-3 mRNA and BDNF mRNA expression in L3-6 segments but not in Sol muscle. TrkC and TrkB mRNA tended to decrease in L3-6 but in the Sol muscle TrkB mRNA decreased and TrkC mRNA strongly increased showing sensitization of the Sol muscle to NT-3 signaling. The possibility of increasing NT-3/TrkC signaling in the neuromuscular system, with minor effects on BDNF/TrkB signaling, by selective stimulation of peripheral nerve, which in humans might be applied in non-invasive way, offers an attractive therapeutic tool. Supported by N N 401 0480 33, BIOIMAGINE grants.