A BRAIN-DERIVED NEUROTROPHIC FACTOR (BDNF) RELATED SYSTEM IS INVOLVEDIN THE MAINTENANCE OF THE POLYINNERVATE TORPEDO ELECTRIC ORGAN

Target-derived molecules are essential for the maintenance of neuron s urvival. In the present work, we introduce the electric organ of Torpe do marmorata as a tool for the study of trophic interactions in a poly innervate system. This electric organ maintains a large number of chol inergic terminals on the postsynaptic cell surface. We have observed t hat a soluble extract derived from the electric organ induces the matu ration of Xenopus oocytes injected with presynaptic plasma membranes ( PSPM), indicating that a trophic system may exist. Moreover, we have d etected a p75(NGFR) related protein in PSPM by Western blot analysis. These results suggest the presence of a neurotrophin-related system ma intaining the polyinnervate electric organ. Furthermore, molecular exp eriments showed that the brain-derived neurotrophic factor (BDNF) is t he neurotrophin operating in our model. Using degenerate oligonucleoti des which comprise a conserved fragment of all neurotrophins, we have only amplified by polymerase chain reaction a BDNF fragment. In a simi lar way, we have amplified and cloned a fragment of the TrkB/C high af finity BDNF receptor. The fact that degenerate oligonucleotides only a mplify BDNF allows us to conclude that the polyinnervation is maintain ed by this neurotrophin either alone or in combination with other trop hic factors. (C) 1997 Elsevier Science Ltd.