Synaptogenesis in the Contralateral Primary Motor Area after Focal Brain Infarction in Rats

Abstract

[Purpose] It is not clear whether changes in the neural networks within the primary motor area contralateral to the infarct hemisphere influence the recovery of neurological functions after strokes. Thus, we investigated whether the number of synapses increased within the contralateral primary motor area after brain infarction. [Subjects] Twenty-four Wistar rats (8 weeks old) were randomly allocated to ischemic or control groups. [Methods] Rats underwent middle cerebral artery occlusion surgery (ischemic group) or sham surgery (control group). All rats underwent two kinds of neurological examination on day 1 after surgery and again 2 and 4 weeks after surgery. The expression of synaptophysin and PSD-95 within the contralateral primary motor area was investigated by western blot analysis. [Results] In the ischemic group, the neurological scores at 4 weeks after surgery were significantly better than those on day 1. There were no significant differences between the two groups in the expression of synaptophysin and PSD-95. [Conclusion] Neurological functions significantly improved after brain infarction, but the number of synapses did not change within the contralateral primary motor area. These findings suggest that changes in synapse number within the contralateral primary motor area are not related to functional improvement after brain infarction.