1. Department of Physiology, Nihon University School of Dentistry,
2. Division of Pathophysiology, Nihon University, 1–8–13 Kanda–surugadai, Chiyoda–ku, Tokyo 101
3. Department of Physiology, Toho University School of Medicine, 521–16 Omori–Nishi, Ota–ku, Tokyo 143, Japan