Molecular Neurobiology Laboratory, Tsukuba Life Science Center, Institute of Physical and Chemical Research (RIKEN), Tsukuba, Ibaraki 305, Japan

Departrnent of Molecular Neurobiology, Institute of Medical Science, The University of Tokyo, Minatoku, Tokyo 108, Japan

Departrnent of Molecular Neurobiology, Institute of Medical Science, The University of Tokyo, Minatoku, Tokyo 108, Japan

Departrnent of Molecular Neurobiology, Institute of Medical Science, The University of Tokyo, Minatoku, Tokyo 108, Japan

Molecular Neurobiology Laboratory, Tsukuba Life Science Center, Institute of Physical and Chemical Research (RIKEN), Tsukuba, Ibaraki 305, Japan
Departrnent of Molecular Neurobiology, Institute of Medical Science, The University of Tokyo, Minatoku, Tokyo 108, Japan