Effects of repetitive transcranial magnetic stimulation on motor cortical excitability and neural function of rats in early period after cerebral ischemia injury / 中国组织工程研究

ABSTRACT

BACKGROUND: It is believed that repetitive transcranial magnetic stimulation (rTMS) may produce such neurophysiological effects as regulating regional cerebral blood flow, neurotransmitters, local metabolism, and neuronal remodeling after nerve tissue injuries. The prognosis ofischemic stroke is related with the cortical function reconstruction in the ipsilateral and contralateral hemisphere of the lesion. Currently studies have not defined whether rTMS can affect the cortical function, protect ischemic neurons and promote motor functional recovery after cerebral ischemia.OBJECTIVE: To investigate the effects of rTMS on rat motor cortical excitability and neural function in acute stage of cerebral ischemia-reperfusion injury.DESIGN: Completely randomized experiment.SETTING: Electroneurophysiological Laboratory of Peking Union Medical College Hospital.MATERIALS: The experiment was completed in the Zoological Research Center of Peking Union Hospital from January to June 2004. Totally 22adult male healthy Wistar rats were randomly divided into treatment group and the control group with 11 in each.METHODS: After determination of the average motor threshold of the right hind limbs, which was 22% of the maximum output, the rats were subjected to middle cerebral artery occlusion for 1 hour followed by reperfusion for 72 hours. At each time point of immediately and at 12, 36 and 60 hours after the initiation of reperfusion, the rats in the treatment group received rTMS treatment (20 Hz, 40% maximum output, 5 seconds for each session with an between-session interval of 2 minutes for a total of 10 sessions), and the site for motor threshold evaluation was used for rTMS stimulation; the rats in the control group recevied no treatment after model establishment. Motor threshold testing was performed in both groups 4 hours after the last session of treatment to avoid immediate-early effects of rTMS on the motor threshold. At 24 and 72 hours of reperfusion, the scores of neural function were recorded according to evaluation systems. All the rats with scores between 1 and 3 were enrolled in statistical analysis were evaluated between.MAIN OUTCOME MEASURES: ① Motor threshold of the rats in both groups before and after injury; ② Neural function scores at 24 and 72 hour reperfusion; ③ Infarct volume at 72 hour of reperfusion.RESULTS: Totally 13 rats entered the final result analysis. Before injury,motor threshold in the treatment and control group was similar (P=0.71),and after the injury, the motor threshold of the control group was 1.49times that of the treatment group but such difference was not statistically significant [(41.62±24.73)% vs (28.00±9.35)%, t=-1.17, P=0.27]. At 24hours of reperfusion, the functional scores of the treatment group and control group were not significantly different (P=0.46), but at 72 hours, the scores of the treatment group were significantly lower than that of the control group (1.60±1.52 vs 7.75±3.62, t=-3.57, P=0.004). The average infarct volume of two groups was (62.00±60.88) mm3 and (20.00±12.41) mm3 at 72 hours of reperfusion, respectively, which, after logarithm transformation,was not significantly different between the two group (t=-1.31, P=0.22),but when the infarct volume was transformed into Log10 values, a significant difference occurred between them (P=0.045).CONCLUSION: rTMS may stabilize and prevent the increment of the motor threshold, time-dependently relieve the neural function disability and reduce the infarct volume after cerebral ischemia-reperfusion injury.