1. Department of Animal Science, Graduate School of Agricultural Science, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe, Hyogo 657-8501, Japan
2. Department of Anatomy, Tokyo Medical University, 6-1-1 Shinjuku, Shinjuku, Tokyo 160-8402, Japan
3. Division of Drug and Structural Research, Life Science Research Center, University of Toyama, 2630 Sugitani, Toyama 930-0194, Japan
4. Departments of Anatomy and Neurobiology, Faculty of Medicine, Kagawa University, 1750-1 Ikenobe, Miki-cho, Kagawa 761-0793, Japan