1. Department of Physiology, Yamaguchi University School of Medicine, Ube, Yamaguchi 755
2. Department of Otolaryngology, Yamaguchi University School of Medicine, Ube, Yamaguchi 755
3. First Laboratory, Medical Research Laboratories, Taisho Pharmaceutical Co. Ltd., Ohmiya, Saitama 330, Japan
4. Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA