Affiliations: Group of Neuroplasticity and Regeneration, Institute
of Neurosciences and Department of Cell Biology, Physiology and Immunology,
Universitat Autònoma de Barcelona, E-08193 Bellaterra, Spain. Centro de
Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas
(CIBERNED), Spain
Abstract: Purpose: To evaluate the effects on locomotion and lumbar motoneuron
function after a contusion to the midthoracic spinal cord of the rat. Methods: Five animals received a moderate contusion on T8, and over 28 days
postoperation (dpo) locomotion and motor electrophysiological outcome were
compared with five sham-operated animals. Results: At 28 dpo, the contused animals supported their body weight (BBB score =11.5 ± 0.5)
and stepped uncoordinatedly. Motor evoked potentials recorded in the tibialis
anterior (TA) and plantar muscles (PL), and longitudinal interlimb reflexes
recorded in the TA muscles were abolished. The M wave recorded in the TA showed
a decrease in amplitude by 7 dpo, which remained invariable until the end of
the evaluation (88 ± 3% of {preoperative} values), whereas in the PL
muscle it was not affected. Injured animals presented hyperreflexia, as shown
by an increased H/M ratio. Histological analysis showed similar number of
retrogradely traced TA motoneurons between groups, and that contused animals
presented hypertrophied astrocytes in the most rostral but not caudal segments
of the lumbar enlargement. Conclusion: These results indicate that after
contusion to the thoracic spinal cord, the lumbar segments undergo structural
and functional changes, following a rostro-caudal gradient extension.
