1. Department of Pharmacology, School of Medicine, Pusan National University, Yangsan 626-870, Korea.
2. Department of Neurosurgery, School of Medicine, Konkuk University, Chungju 380-704, Korea.
3. Laboratory of Microbiology, College of Veterinary Medicine and Bio-Safety Research Institute, Chonbuk National University, Jeonju 561-756, Korea.