title: The impact of training and neurotrophins on functional recovery after complete spinal cord transection: cellular and molecular mechanisms contributing to motor improvement.
abstract: Beneficial effects of locomotor training on the functional recovery after complete transection of the spinal cord indicate that in chronic spinal animals spontaneous recovery processes are enhanced and shaped by the training. The mechanisms of that use-dependent improvement are still not fully understood. This review tackles three aspects of this issue: (1) neurochemical attributes of functional improvement showing that concentrations of excitatory and inhibitory amino acids in the lumbar spinal segments, which were changed after transection, normalize after the training, or even raise beyond normal. As it does not translate to functional equilibrium between excitatory and inhibitory neurotransmission and may lead to hyperexcitability, the postsynaptic mechanisms which might be responsible for the hyperexcitability are discussed, including (i) dysfunction of K(+)-Cl(-) cotransporter KCC2, which controls the strength and robustness of inhibition, and (ii) altered function of 5-HT2 receptors, which may be targeted to restore KCC2 activity and intrinsic inhibition; (2) morphological changes of lumbar motoneurons and their inputs related to functional improvement of spinal animals, pointing to use-dependent diminution/reversal of the atrophy of the dendritic tree of the hindlimb motoneurons and of their synaptic impoverishment, which in paraplegic animals differs depending on the degree of disuse of the muscles; (3) the role of neurotrophins in motor improvement of spinal animals showing, that increases in neurotrophins due to training or due to efficient viral vector-based transgene expression, that might be responsible for the enrichment of the dendritic tree, elongation of processes and influence neurotransmitter systems in the areas subjected to plastic modifications after injury, correlate with improvement of locomotor functions.
authors.affiliation: Laboratory of Reinnervation Processes, Department of Neurophysiology, Nencki Institute of Experimental Biology PAS, Warsaw, Poland, m.skup@nencki.gov.pl.
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Skup
authors.forename: Ewelina
authors.initials: E
authors.lastname: Ziemlinska
authors.forename: Olga
authors.initials: O
authors.lastname: Gajewska-Wozniak
authors.forename: Rafał
authors.initials: R
authors.lastname: Platek
authors.forename: Anna
authors.initials: A
authors.lastname: Maciejewska
authors.forename: Julita
authors.initials: J
authors.lastname: Czarkowska-Bauch
mesh_terms: D000818:Animals; D005081:Exercise Therapy / Q000379:methods*; D006801:Humans; D009414:Nerve Growth Factors / Q000378:metabolism / Q000627:therapeutic use*; D020127:Recovery of Function / Q000187:drug effects* / Q000502:physiology; D013119:Spinal Cord Injuries / Q000188:drug therapy* / Q000534:rehabilitation*
chemical_list: D009414:Nerve Growth Factors