1. Department of Obstetrics and Gynecology, First Affiliated Hospital of China Medical University, Shenyang, Liaoning 110001, P.R. China
2. Department of Neurology, First Affiliated Hospital of China Medical University, Shenyang, Liaoning 110001, P.R. China
3. Department of Physiology, College of Basic Medical Science, China Medical University, Shenyang, Liaoning 110001, P.R. China