1. Department of Demyelinating Disease and Aging, National Institute of Neuroscience, NCNP, 4-1-1 Ogawahigashi, Kodaira, Tokyo 187-8502, Japan
2. Saigata National Hospital, Saigata, Nakakubikigun 949-3100, Japan
3. Tokyo Institute of Psychiatry, Kamikitazawa, Setagaya, Tokyo, Japan
4. Yamagata University Faculty of Medicine, Yamagata 990-9585, Japan
5. Institute de Pharmacologie Mol\'eculaire et Cellulaire, CNRS, Valbonne 06560, France