Abnormal reflexes associated with spasticity are considered a major determinant of motor impairments occurring after
stroke; however, the mechanisms underlying post-
stroke spasticity remain unclear. This may be because of the lack of suitable rodent models for studying spasticity after cortical
injuries. Thus, the purpose of the present study was to establish an appropriate post-
stroke spasticity mouse model. We induced photothrombotic injury in the rostral and caudal forelimb motor areas of mice and used the rate-dependent depression (RDD) of Hoffmann's reflex (H-reflex) as an
indicator of
spastic symptoms. To detect motoneuron excitability, we examined c-fos
mRNA levels and c-Fos immunoreactivity in affected motoneurons using quantitative real-time reverse transcription PCR and immunohistochemical analysis, respectively. To confirm the validity of our model, we confirmed the effect of the anti-spasticity
drug baclofen on H-reflex RDDs 1 week post
stroke. We found that 3 days after
stroke, the RDD was significantly weakened in the affected muscles of
stroke mice compared with
sham-operated mice, and this was observed for 8 weeks. The c-fos
mRNA levels in affected motoneurons were significantly increased in
stroke mice compared with
sham-operated mice. Immunohistochemical analysis revealed a significant increase in the number of c-Fos-positive motoneurons in
stroke mice compared with
sham-operated mice at 1, 2, 4, and 8 weeks after
stroke; however, the number of c-Fos-positive motoneurons on both sides of the brain gradually decreased over time.
Baclofen treatment resulted in recovery of the weakened RDD at 1 week post
stroke. Our findings suggest that this is a viable animal model of post-
stroke spasticity.