The
mechanism behind constraint-induced movement therapy (CIMT) in
promoting motor recovery after stroke remains unclear. We explored the
bilateral structural and functional reorganization of the brain induced
by CIMT after left middle cerebral artery occlusion (MCAO) in rats. CIMT
started on the 8th day (D8) after MCAO surgery and lasted
for 3 weeks. Skilled walking was assessed by Foot-Fault tests. The
efferent neuron network innervating the paralyzed forelimb was labeled
by pseudorabies virus (PRV) to explore neuron recruitment. Synapsin Ⅰ
was used as an indicator of the number of synapses. Additionally, C-fos
expression 1 h after walking was detected to explore the activation of
the brain. As a result, CIMT significantly improved skilled walking and
elicited more neuron recruitment into the innervating network of a
paralyzed forelimb in the contralesional rather than the ipsilesional
motor cortex and red nucleus. CIMT also increased the synapse number in
the contralesional cortex but there was no corresponding effect in the
intact ipsilesional cortex. Furthermore, MCAO decreased ipsilesional
motor cortex activation, but CIMT partially compensated for this by
increasing the number of activated neurons (c-fos+) in both
the left and right motor cortex. In conclusion, the contralesional motor
cortex and red nucleus might play more important roles than
corresponding ipsilesional regions in structural reorganization during
CIMT-induced motor recovery after stroke. However, CIMT promotes
bilateral motor cortex activity without a side preference.
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