1. Institute of Laboratory Animals, Graduate School of Medicine, Kyoto University, Yoshidakonoe-cho, Sakyo-ku, Kyoto 606-8501, Japan
2. Department of Psychiatry and Neurology, Asahikawa Medical College, 2-1-1-1 Midorigaoka higashi, Asahikawa 078-8510, Japan
3. Institute of Animal Reproduction, 1103 Fukaya, Kasumigaura 300-0134, Japan