Complementary actions of BDNF and neurotrophin-3 on the firing patterns and synaptic composition of motoneurons.
Neurotrophins, as target-derived factors, are essential for neuronal survival during development, but during adulthood, their scope of actions widens to become also mediators of synaptic and morphological plasticity. Target disconnection by axotomy produces an initial synaptic stripping ensued by synaptic rearrangement upon target reinnervation. Using abducens motoneurons of the oculomotor system as a model for axotomy, we report that trophic support by brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3) or a mixture of both, delivered to the stump of severed axons, results in either the prevention of synaptic stripping when administered immediately after lesion or in a promotion of reinnervation of afferents to abducens motoneurons once synaptic stripping had occurred, in concert with the recovery of synaptic potentials evoked from the vestibular nerve. Synaptotrophic effects, however, were larger when both neurotrophins were applied together. The axotomy-induced reduction in firing sensitivities related to eye movements were also restored to normal values when BDNF and NT-3 were administered, but discharge characteristics recovered in a complementary manner when only one neurotrophin was used. This is the first report to show selective retrograde trophic dependence of circuit-driven firing properties in vivo indicating that NT-3 restored the phasic firing, whereas BDNF supported the tonic firing of motoneurons during eye movement performance. Therefore, our data report a link between the synaptotrophic actions of neurotrophins, retrogradely delivered, and the alterations of neuronal firing patterns during motor behaviors. These trophic actions could be responsible, in part, for synaptic rearrangements that alter circuit stability and synaptic balance during plastic events of the brain.
Davis-López de Carrizosa
María A
MA
Departamento de Fisiología y Zoología, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain.
Morado-Díaz
Camilo J
CJ
Tena
Juan J
JJ
Benítez-Temiño
Beatriz
B
Pecero
María L
ML
Morcuende
Sara R
SR
de la Cruz
Rosa R
RR
Pastor
Angel M
AM
D000200:Action Potentials / Q000187:drug effects*; D000704:Analysis of Variance; D000818:Animals; D019771:Axotomy / Q000379:methods; D019208:Brain-Derived Neurotrophic Factor / Q000494:pharmacology*; D002227:Carbazoles / Q000494:pharmacology; D002415:Cats; D002795:Choline O-Acetyltransferase / Q000378:metabolism; D004347:Drug Interactions; D004558:Electric Stimulation / Q000379:methods; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005133:Eye Movements / Q000187:drug effects; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D026121:Indole Alkaloids / Q000494:pharmacology; D009046:Motor Neurons / Q000187:drug effects* / Q000378:metabolism; D009416:Nerve Regeneration / Q000187:drug effects; D020933:Neurotrophin 3 / Q000494:pharmacology*; D011149:Pons / Q000166:cytology; D055366:Synaptic Potentials / Q000187:drug effects; D009435:Synaptic Transmission / Q000187:drug effects*; D016708:Synaptophysin / Q000378:metabolism; D013997:Time Factors; D050496:Vesicular Glutamate Transport Proteins / Q000378:metabolism
D019208:Brain-Derived Neurotrophic Factor; D002227:Carbazoles; D004791:Enzyme Inhibitors; D005904:Glial Fibrillary Acidic Protein; D026121:Indole Alkaloids; D020933:Neurotrophin 3; D016708:Synaptophysin; D050496:Vesicular Glutamate Transport Proteins; C049985:staurosporine aglycone; D002795:Choline O-Acetyltransferase