Objective To investigate the expression of occludin,ZO-1,MMP-2,and MMP-9 in cerebral microvasculature following Pulse Electromagnetic Field (PEMF) induced BBB permeability change.Methods Sprague-Dawley rats were randomized into PEMF and sham exposed groups (n=8).After exposure to PEMF at 0.5,1,3,6,and 12 h,BBB permeability was measured by Evans-Blue extravasation.The expression of occludin,ZO-1,MMP-2,and MMP-9 were detected by real-time quantitative reverse transcriptase PCR and western blotting.MMP-2 and MMP-9 activity were detected by EnzChek gelatinase assay.Results Compared with the sham group,PEMF exposure led to increased permeability of the BBB to EB,which was prolonged after exposure.BBB permeability became progressively more severe,and recovered at 6 h.The gene and protein expression of occludin and ZO-1 were significantly decreased,while MMP-2 and MMP-9 expression were significantly increased after exposure to PEMF.All levels of expression recovered 12 h following PEMF.Conclusion Changes to BBB permeability were related to the alteration expression of tight junction proteins and matrix metalloproteinase after exposure to PEMF.