Effects of repetitive transcranial magnetic stimulation on cognitive function in rats with chronic cerebral hypoperfusion

Objective To observe the effects of repetitive transcranial magnetic stimulation (rTMS) on cognitive function in rats with chronic cerebral hypoperfusion. Methods The animal model of chronic cerebral hypoperfusion was established in 30 Sprague-Dawley rats by surgically induced bilateral common caroid artery stenosis, who were then divided into a control group and a treatment group. The rats in the treatment group were administered with 20 Hz rTMS 4 weeks postoperation for 7days. Another 10 rat subject to sham operation served as blank controls. The cognitive function was assessed by Morris water maze (MWM) at the time points of 2nd, 3rd, 4th and 5th days after ending of the 4 weeks of reatment. The morphologic changes of hippocampus neurons were observed with HE staining. The apoptosis was examined by TUNEL, the expression of Bcl-2 or Bax protein was determined using immnunohistochemistry assay. Results At all the time points the MWM escape latency in the rTMS group was shorter than that in the control group (P<0.01). The percentage of crossing the corresponding platform during the same time period in platform quadrant in the rTMS group was significant higher than that in the control group (P<0.01). Compared with the control group, the treatment group demonstrated significantly decreased percentage of neuronal apoptosis (P<0.05), as well as increased expression of Bcl-2 protein (P<0.01) and reduced expression of Bax protein (P<0.01). Conclusion rTMS can improve the cognitive dysfunction in rats caused by chronic cerebral hypoperfusion, probably through inhibiting neuronal apoptosis in hippocampus region. Key words: Repetitive transcranial magnetic stimulation; Chronic cerebral hypoperfusion; Hippocampus; Cognitive function